Electronics 2 Test 1 & Test 2
what are the two separate small signal models you can use? note polarity
ID is the DC current notice it goes from drain to source, so PMOS goes in the opposite direction ro only occurs when lamda!=0, or channel modulation is taking place
voltage line regulation formulas both ways
first is % second is %/V
what is the gain formula?
for model when r0 !=0 A = vo/vin vo = voltage over the output resistance ONLY vin can include source plus any current and reistances with respect to ground vin is vgs
how to find output resistance of a mosfeT?
itest - gmvgs - i0=0 vgs = vtest itest = gm vtest + vtest/r0 vtest/itest = 1/gm+r0 = r0 Ro usually
what is the small signal equivelant of a diode connected mosfet? (or mosfet with drain connected to gate with DC source or drain connected to ground )
just insert on drain side
how do you want to treat a source which goes negative?
keep the polarity given, just assume that it will be neagative at the opposite end of the diode, you dont want to treat vi as negative, just make current stay the same direction and you can assume vi will always be there becasue if vi was -5, then it would be -5 on the cathode of it still so dont make the variables negative, treating it going negative in the same direction as the positive, and a diode flipped will have a lower voltage on the cathode than the annode which is 0 volts and will turn on
if you see a circuit attenuates and uses a mosfet to turn on, what does that mean? REVIEW
ron = rds voltage divide on RL RL/RL+Ron
if not given, do you assume saturation or triode region?
saturation
what is the schematic of a CMOS?
separated and isolated transistors by thick oxide as an insulator
formula for the current to pass through a pn junction
(divide by A to get the current density J0 because J0 = I0/A Dn/Dp= electron//whole diffusion coeffuicent Ln/Lp = average time of reconstruction of electrons/wholes np0 - electron concentration on p side =ni^2/Na pn0 - whole concentration on n side = ni^2/Nd Na = acceptor concentration Nd = donor concnetraiton wd = depletion width
what do you need to rememer every time a mosfet is in triode?
there is an rds!
What is a diode?
- special device made from semi-conductor material, e.g. silicon - it is used to regulate the potential difference in circuits - it lets the current flow freely in one direction but not the other as there is a very high resistance in the reverse direction - a pn junction, nonlinear device the pn junction can conduct substantial current in the forward direction and almost no current in the reverse direction A diode is a device that allows current to flow in only one direction. When a so-called forward bias (a voltage in the "forward" direction) is applied, current flows freely through the device. When the voltage is applied in the opposite direction (called a reverse bias), no current flows. p type - acceptors, they will bring in electrons to fill wholes n type - donors, they will give electrons creating holes
what is 1/gm || r0 or 1/gm+ro? REVIEW
1/gm
constant voltage applied gates are replaced with what?
1/r most of the time, they are in paralell with drain due to the source voltages shorting out!!!
how do you solve for the current in an ideal diode?
10 V/ 1000 ohm = 5 mA
what is the formula for Is? range?
10^-19 through 10^-9 A
how to deduce this equation w/l1=1.5w/l2=20
20/13.3 = w/l2 w/l1 = 20 w/l1 / w/l2 = 1.5
what is the transcoductance of the mosfet?
AC parameters gm = id/vgs = output current/input voltage
OUTPUT RESISTANCE OR INPUT RESISTNACE MEANS TO DO WHAT?
APPLY A TEST SOURCE
what are the charactersitcs of each mosfet amplifier? CALCULATOR, EXPLAIN HOW YOU GET EACH
Av0 = open circuit voltage gain Av = voltage gain of amplifier proper Gv = overall voltage gain Ro = output resistance usually you can take the magnitude of the gain, CS and CG you can use hybrid pie whereas CD you use T model
current going through diode equation
Id = Is e^vd/vt
step up vs step down transformers
IfNs>Np, the device is a step-up transformer because it steps the primary's voltageVp up to a higher voltage Vs. Similarly, if Ns <Np, it is a step-down transformer. so a 15:1 turn ratio is a step down by 15 (divided the original by 15) voltage is over the entire circuit
how to find max and average current going through output resistor? what is IL?
Il = Vp/R
what is true when trying to find the current of a zener diode?
Iz>Izk Vz>Vz0 vz0 occurs at Izt
which way does the current flow in NMOS vs PMOS?
NMOS - drain to source PMOS - source to drain this is how you can idenitfy drain and source if given a current flow direction and type of mosfet
what is the schematic of a PMOS and how does it work? threshold voltage? current direciton?
PMOS vt<0 NMOS vt >0 NEGATIVE GATE DRAIN AND THRESHOLD VOLTAGE Vgs<0, VDs<0, causing current to go to the drain in a p type
parallel resistance
Req = (1/r1+1/r2+1/r3)^-1 or
what is the theroem of superposition? how it applied?
The Superposition Theorem states that a circuit can be analyzed with only one source of power at a time, the corresponding component voltages and currents algebraically added to find out what they'll do with all power sources in effect. To negate all but one power source for analysis, replace any source of voltage (batteries) with a wire; replace any current source with an open (break). this can be used to determine hte voltage output when converting zener diode to a voltage source and resistor
Determine the current ID and the diode voltage VD for the circuit in Fig. 4.10 with VDD =5 V and R=1 k. Assume that the diode has a current of 1 mA at a voltage of 0.7 V with 20k ohm resistor . *NOTES* base use piecewise linear model to calculate vD and Id
V = IR, and then treat the bottom as ground and do loop analysis basically to solve for Id
what is the battery plus diode model? what determines this model? REVIEW!!
V>Vdn, on V<Vdn, off (usually means when a voltage drop over the diode occurs) if there is a voltage drop over a diode, it will always hold this voltage reguardless of the current on voltage supplied to the circuit!
what is the AC small signal voltage approximation derivation? *REVIEW* 4th model!!!!
VD = DC (upper upper) vD(t) = instananoeous (upper lower) vd(t) = AC (lower lower)
what is Vov?
Vgs - Vth
How does biasing work with a constant voltage supply applied to the gate?
Vgs = Vg - Vs Vg is constant, and Vs is the variable so Vgs is now variable Vg = R2(R1+R2)*vdd We know the q point will change
schematic of NMOS transistor and current direction
Vgs> Vt but Vt is positive, small Vds
zhener diode output waveform explain and review!
Zhener diode is usually placed in reverse bias because it will prevent current flowing through the circuit up to a certain voltage it has a specific breakdown voltage, and once it reaches that breakdown voltage and goes above, the voltage drop over the zener diode remains constant and current flows through the circuit one the negative input starts, there is a voltage drop over the zener diode, just the same as a regular diode, which needs to be met before it can begin conducting
regions of operation for PMOS REVUEW WHEN DOES A CHANNEL FORM? can source side have relationship with drain side?
absolute vlaue of Voverdrive Vsg and Vsd are positive Vs is connected to source Vov = Vsg - Vt Vgs<Vt |Vgs>Vt|, if less than called cutoff region Vth <0 the source of a p channel can be connected to VDD is current is running from source to drain (drain will hten be on negative side
How do you maintain bias stability? what else does this do?
adding a resistor, Rs, on the source side adding Rs also promotes negative feedback by performing load line equation, you are able to find the correct certain relations between Vth and Id
Explain a bridge rectifier What is its PIV?
alternative way to full wave rectifier without center tapped transformer v0 is less than vs by 2 diode drops instead of 1 in a full wave rectifier positive cycle Vd3(reverse) = v0+Vd2 (forward Vs - 2vd + Vd = Vs-Vd also just put in forward bias ahd open circuit other two, you can find PIV over diode three basically so V0 will contantly be getting power in the SAME DIRECTION!!!n DC
what is the body effect of a mosfet?
an incremental voltage, VSB, gives rise to an incrementeal chane in Vt, which in turn results in an incremental change in id even though Vgs is constant, and the body control id acting as another gate for the mosfet Vsb = voltage between source and body , given madani said phif and gamma = .4V given
how do you find input resistance to a mosfet?
apply to side as if looking inwards do KCL Rin = 1/gm usually
circuit symbol of a CMOS - REVIEW
assume always pmos then nmos - source drain drain source
when we are designing for a current source, what things are we safe to assume?
assume w/l and iref, not the vgs?
NFET circuit symbol how to remember
electrons to drain current to source normal (electrons go from source to drain) drain is always positive relative to the source in an nfet
What is the battery plus resistor model? REVIEW
basically able to remove the expontial curve of the diode and approximate using the slope of 1/Rd which originates at Vdn - note Vd is over the whole model!!
explain why these models are the way they are
because of the labeling
how to find average output voltage for AC input? (REVIEW
change limits to terms of theta where the value is present and this is referring to the half wave recrifier (THETA IS RADIANS AND IT IS WHERE IT STARTS CONDUCTONG SO THATS WHY YOU DO ONLY OVER 1 CYCLE https://www.slader.com/discussion/question/a-full-wave-rectifier-circuit-with-a/\ CALC IN RADIANS MODE vavg = 1/T intgreal from 0 to 2pi V0 dtheta and then change to this form
what is current source biasing?
current source added to load line node, so that means the current through the current source is equal to Id
PFET circuit symbol
current to train, electrons to source
what is the regualtion output? REVIEW
deltaVout/Vout *100
how does the IV characterics act for a small NFET drain voltage, vds? why?
device has a linear resistance in small vds which is controlled by Vgs
alternative way for finding current passing through diode given voltage drop
do the subtraction because the diode will not be on until this voltage across each diode is applied (BASICALLY JUST ACT LIKE THE VOLTAGE SOURCE IS BEHIND THE DIODE BUT THE TOTAL DROP IS APPLIED OVER THE WHOLE THING)
What is Id in the saturation region? what is the saturation region? explain it
drain current saturates, channel becomes pinched off but does not become blocked - current continues to run through the channel saturation = Vds>Vgs-Vt kn =un Cox
mesh analysis review
draw meshes (current directions) for each independent loop & express currents in shared branches in term of mesh currents apply kvl to get loop equations solve your set of simultaneous equations number of loops is number of equations//number of unknowns voltage drops are pos from neg = -v voltage gains going from neg to pos = +v, use voltage drops of resistances
what to remember about different transistors in the same cirucit?
each have their own transconductance and W/L values
explain the traveling of electrons and the electric field when voltage is only applied to the gate?
electric ifeld runs down (positive to negative) top of gate is like capacitor with positve charges and oxide like insulator in the middle and bottom has negative charges causing electric field to form (bottom plate electrons caused by channel electorns) Fe- = -qE electrons opposte direction of electric field, so E = V/d so electrons will accumulate near the service, and then an n region is created connecting the source and the drains so if a voltage source is applied to the source or drain, a current appears across the channel, also calledan inversion layer
votlage drop of parallel branches are___ and the total voltage drop in a ground is equal to the source also, when currents break from a parent branch, the original branch is the sum of both the current s
equal!!
what does diode connected mosfet mean? what do you do when you see it?
gate connected to drain or ground connected to grain replace with 1/gm||r in small signal
what is the small signal approximation composed of, and how does it work?
iD = ID +id iD = ID+ uncoxW/l(VGS-VTH)vgs upper = DC/lower = AC by treating vgs<<2(Vgs-vth), which vgs^2 becomes 0, which is non linear, becomes a linear model y = A+Bx A and B are constants, where x is the vgs on the AC side
what is the configuration of a CMOS inverter, and what does it mean?
input negative voltage to the gates, outputs positive voltage and vice versa
whhat is the source/drain configuration for a CMOS?
it can be either way
how does a diode placed backwards act under reverse bias?
it conducts a POSITIVE voltage
what does it mean if the gate is connected to the drain voltage?
it is always in saturation since Vds= Vgs
What is Id in the triode region of the diode? what is the triode region?
kn' = un Cox Vov = VGs - Vt triode : Vds <Vgs-Vt non pinched off channel so Vds is increased but not greater than Voverdrive, MOSFET n channel Acts like a resistor in the triode region
what is the Q point? example
load line equation = kvl from drain to source and set equal to 0, and then you can plot this on a Vdd vs Id graph, by setting Vds and id to 0 to solve for the two values, and wherever it cross the saturation line is your Q point - it is Vds, not vgs
nfet vs pfet
n channel has n type ground and source and p type subtrate - NFET p channel has p type ground and source and n type subtrate - PFEt
cmos inverter small signal CATCH?
only if input ac is applied to both if one is applied to a DC source, it becomes open circuited due to the superposition principle both r0s will be present though for output resistance as well
how do you find the peak inverse voltage?
put the diode under a reverse bias (opposite -Vpk) which will make open circuit and see voltage over the diode and it is |PIV| and it is the Vannode - Vcathode, and cathode voltage wil probably be posiotve
what to remember about the KVL of a MOSFET circuit?
remember to include VDs 10k*id+Vds-2.5
if dealing with a CMOS and one is not connected to the AC source but it is in drain to gate connection, what do you do?
replace it with 1/gm1 as a resistance
two diode connected pmos loads and what to do WHEN YOU SEE THEM REVIEW
replace them with 1/g || r to prove this, just apply test voltage and currents etc
how long does an ideal diode conduct in a half wave rectifier? what percent is it on for a battery plus diode model?
so 1/2 cycle is 180* pi = 180 for entire period it is 360* 2pi = 360 basically just find the point where the voltage of the diode turns on Vs^ is the input sinusoidal signal (PEAK VALUE COMING IN, not -the .7)
labels of silicon based mosfet
source and drain are relative t ox is usually SiO2, and is the insulator or dieletric layer body means substrate drain is alway spositive voltage compared to the source
remember, if the voltage for a diode is not met, it becomes an open circuit so the voltage of the diode is the open circuit! diode voltage cant exceed the drop voltage, once the input voltage exceeds the drop, it begins conducting but the dioe will hold that voltage and never go higher
t>t2 is an open circuit t1<t<t2 is shrot circuit (negative voltage on cathode allows current to pass)
arrows going down and marker values and how to treat the marker values
the little bubbles are not sources, rather just saying this is the voltage after cross the diode and continues for the rest of the branch
if you are looking at voltage before it cross the reisstor, it is positive if you are looking after it cross the resistor, it is negative review example what does it mean for the node between two mosfets if two mosfets in series are matched?
the node between them will have to be 0 v (V0)
what are some clipping, limiting circuits? REVIEW 4 scenarios! AND ZENER
the v0 is just the voltage drops across the diodes which it allows to pass depending on input voltage peaks of input are clipped, for zener, just say whatever Vz for the reverse bias and that is the value it holds
how does voltage act in an open circuit?
the voltage of the source is the voltage over the open circuit since there is no current flowing through any of the resistors but must be connected to the part with tht resistor
what does it mean if you have two mosfets in series? REVIEW
they have the same current running through both, so you can set them equal to each other if they are matched, same current will go through each!
what id the current Id for a small applied Vds?
un = electron mobility
explain small signal is resistors are on the gate explain output and input REVIEW
vin = vgs Vout = -gmvgs * r1 || r2 etc- input resistance
Explain the two equations for channel length modulation effects? when does it occur?
when lamda = 0, both saturation currents are the same as before, which means no modulation effects so R0 = 1/lamda*id=Va/id channel length modulation only occurs when lamda is not equal to 0 and when the mosfets are in saturation or pinchoff which means Vds>Vgs-Vth
how do you solve a CMOS inverter which only has an AC source connected to one gate? NOTES
you can find id because the second one acts like a current source, and that will then become open circuited, but, its resistor value will still be there
Explain a full wave rectifier
-this is assuming the diode still has a voltage drop of .7 V so thats why it is delayed -positive - D1 has forward bias so on -negatie - D2 has forward bias and both pas current to v0 uses center tapped transformer notice how both sides are positve!! positve due to negative voltage going opposite direction?
make sure you know where the open circuit voltage is over if v0 is not over the diode, the open circuit voltage does no apply to V0! REVIEW REET
AHHHHHHH
How do we expect a capacitor to act for amplifiers?
Coupling capacitor in the range of 1uf to 100uF DC = CC is open circuit low freuqnecy = OC midband = shortcircuit high frequency = ?
what is the magnitude of the electron charge and what is the oxide capactiance(COX)?
Cox=3.45E-11/tox, and tox is the oxide thickness F/m^2 units
what happens when a small voltage is applied to the drain for an NFET? (drain is usually positive) why is it called a drain?
Having induced a channel, we now apply a positive voltage vDS between drain and source, as shown in Fig. 5.3. We first consider the case where vDS is small (i.e., 50 mV or so). The voltage vDS causes a current iD to flow through the induced n channel. Current is carried by free electrons traveling from source to drain (hence the names source and drain). By convention, the direction of current flow is opposite to that of the flow of negative charge. Thus the current in the channel, iD, will be from drain to source, as indicated in Fig. 5.3. called a drain because electrons from the positive side come to the drain from the source -this channel acts as a resistor of high resistance =id = is since iG is 0 due to the insulator -electric field runs horizontally, creating current
n-type vs. p-type
Instead of doping a semiconductor with donors, one could add impurities that have fewer electrons in the outer shell than the replaced atoms.Consider the case of Si (four valence electrons) doped with boron, which has three valence electrons. Figure 2.8a shows how doping Si with boron will produce a p-type material. Boron is called an acceptor insilicon. We know that atoms in general like to fill their outer shells, even if it means sharing electrons. The silicon atoms near the boron atom would like to have eight electrons apiece, but they are collectivelyone electron short. If an electron from a nearby silicon atom should occupy that state, the bond becomes full, but the boron atom becomes negatively charged since it now has more electrons than protons. Since the electron most likely came from some nearby covalent bond, a hole was left behind. atom cant move but the whole can accePtor (P type) - Ef closer to Ev no hole created in this case, phopsphorus is chained down, but it is a donor (group 5) with the free electron easily excited to the conduction band and phophorus is ionized and stuck in place.The donor ion resembles the hydrogen atom in which electron is bound to the single positive charge hydrogen nucleus .N doNor - Ef closer to Ec
What is a current mirror and what does it introduce? what else is it called? what state is it in?
Io = (w2/l2)/(w1/l1) * Iref if the aspect ratios are the same, it basically becomes a current source SOLVE IS AF THEY WERE EQUAL, AND THEN APPLY W/L2 = W/L1 TO SO SOLVE if 1 is in saturation, then the other is as well (STEERING MOSFET
explain and gates and or gates using diodes
OR - Thus the output will be high if one or more of the inputs are high. AND - output is high if all inputs are high consider a positive-logic system in which voltage values close to 0 V correspond to logic 0 (or low) and voltage values close to +5 V correspond to logic 1 (or high). The circuit in Fig. 4.5(a) has three inputs, vA, vB, and vC. It is easy to see that diodes connected to +5-V inputs will conduct, thus clamping the output vY to a value equal to +5 V. This positive voltage at the output will keep the diodes whose inputs are low (around 0 V) cut off. basically for an or gate, when 1 is high and the others have outputs have voltages higher on the cathode side, they will not conduct and will take the highest voltage - only one input must be on for it to be able to conduct through the diode - if the multiple inputs are on, all voltage is dissipated through the resistor basically only one needs to be on to begin conducting, or higher than the other side becasue rest of voltage will be lost by the LED itself and gate - if any of the gates are lower than input DC voltage, current will flow through them, and the lowest one will change it the most when flowing through becoming a short with all flowing all curernt to ground if you make all cahtodes of the diodes equal to source voltage, none will become shorts( all will become open circuit), and then the annode of the diode leading to the LED will turn into a short and turn the led on when all three inputs are high, or on for the and gate, no current is able to pass and is a forward bias on LED allowing current to flow if 1 is low, or shorts and drains all current if all are low, all LEDS take in current due to reverse bias (low is 0 v on cathode side) https://electronics.stackexchange.com/questions/256675/how-to-solve-a-simple-diode-gate-question-from-sedra-and-smith-exercise-4-4
Golden Rules Op amps
Op Amp Golden Rules (memorize these rules) 1) The op amp has infinite open-loop gain. 2) The input impedance of the +/− inputs is infinite. (The inputs are ideal voltmeters). The output impedance is zero. (The output is an ideal voltage source.) 3) No current flows into the +/− inputs of the op amp. This is really a restatement of golden rule 2. 4) In a circuit with negative feedback, the output of the op amp will try to adjust its output so that the voltage difference between the + and − inputs is zero (V+ = V−) The gain of an op amp signifies how much greater in magnitude the output voltage will be than the input. For example, an op amp with a resistor, RIN, of 20KΩ and a resistor, RF of 100KΩ, will have a gain of 6. This means that the output will be 6 times greater in magnitude than the input voltage. if signal applied to + input, output is in phase if signal applied to - input, output is 180 out of phase
what is simple biasing, the load line equation, and the Q point?
Q point = (Idq, Vdsq) load line equation = kvl from drain to source and set equal to 0, and then you can plot this on a Vdd vs Id graph, by setting Vds and id to 0 to solve for the two values, and wherever it cross the saturation line is your Q point
what is the DC output voltage for a capacitor in paralell with load of a half wave rectifier? REVIEW
The diode conducts for a brief interval, t, near the peak of the input sinusoid and supplies the capacitor with charge equal to that lost during the much longer discharge interval. The latter is approximately equal to the period T. Assuming an ideal diode, the diode conduction begins at time t1, at which the input vI equals the exponentially decaying output vO. Conduction stops at t2 shortly after the peak of vI ; the exact value of t2 can be determined by setting iD =0 in Eq. (4.25). 3. During the diode-off interval, the capacitor C discharges through R, and thus vO decays exponentially with a time constant CR. The discharge interval begins just past the peak of vI . At the end of the discharge interval, which lasts for almost the entire period T, vO = Vp - Vr , where Vr is the peak-to-peak ripple voltage. When CRT, the value of Vr is small. When Vr is small, vO is almost constant and equal to the peak value of vI . Thus the dc output voltage is approximately equal to Vp. Similarly, the current iL is almost constant, and its dc component IL is given by if non ideal Vp = Vp-Vd Vp is the peak voltage over the load
what is the threshold voltage? what is it for an n channel?
The value of vGS at which a sufficient number of mobile electrons accumulate in the channel region to form a conducting channel is called the threshold voltage and is denoted Vt .4 Obviously, Vt for an n-channel FET is positive. The value of Vt is controlled during device fabrication and typically lies in the range of 0.3 V to 1.0 V for the channel to form, VGs must be > VT
what is the input impedance? REVIEW FOR REALLLLLL!!
This refers to the opposition to current flow, in the early stages of amplification, between input 1 and 2 of a differential amplifier. These would be in parallel on the input impedance according to small signal -impedance to the input source to the gate
how does a rectifier with a capacitor in parallel work? REVIEW
To see how the rectifier circuit with a filter capacitor works, consider first the simple circuit shown in Fig. 4.26. Let the input vI be a sinusoid with a peak value Vp, and assume the diode to be ideal. As vI goes positive, the diode conducts and the capacitor is charged so that vO = vI . This situation continues until vI reaches its peak value Vp. Beyond the peak, as vI decreases, the diode becomes reverse biased and the output voltage remains constant at the value Vp. In fact, theoretically speaking, the capacitor will retain its charge and hence its voltage indefinitely, because there is no way for the capacitor to discharge. Thus the circuit provides a dc voltage output equal to the peak of the input sine wave. This is a very encouraging result in view of our desire to produce a dc output. Next, we consider the more practical situation where a load resistance R is connected across the capacitor C, as depicted in Fig. 4.27(a). However, we will continue to assume the diode to be ideal. As before, for a sinusoidal input, the capacitor charges to the peak of the input Vp. Then the diode cuts off, and the capacitor discharges through the load resistance R. this is assuming the diode turns on for the positive portion and the capcitor voltage is reached, and then voltage begins to decrease and capacitor retains its charge causing reverse bias, shutting diode off until its next cycle to recharge capacitor to maximum and allows for DC component diode is only on between t1 and t2, and when off capacitor discharges through the resistor it is a half wave rectifier with a capacitor paralell to the load!
what does the channel length modulation bring about? explain it
Va = early voltage = 1/lamda just know 1 over lamda/id this occurs from channel length modulation or you can use Va/ID (id is regular saturation current and Va = 1/lamda) pinch off region moves farther from the drain when the diode is under saturation increasing Vds>>VGs-Vt does cause some effects to the channel kn' = unCox
what is a good way to find if in saturation or not if not given Vs?
Vds = Vgs - Vt vs cancels Vd>Vg-Vt
explain the mosfet terminology of Vgs and Vds
Vgs = Vgate - Vs only voltage with respect to ground is the source is grounded Vds = Vd - Vs(voltage over drain - Voltage over source) Ids = drain to source current (for a nfet) Vd includes source and resistor etc
explain small signal is resistors are on the source explain why
Vin = vgs + gms vgs rs Vout = -gm vgs rd rs decreases the gain of the circuit but ads stability
regions of operation summary for NMOS transistor table explain all terms / HOW DOES A CHANNEL FORM? what happens in saturation? rEVIEW -> SATURATION IS >= small VDS triode region?
Vov = Vgs - Vt kn = un Cox VD connected to source, Vs connected to ground!!! curent will remain constant, on Vds will not matter when it is greater than Vds-Vt, and any resistors will not matter either and the diode current will remain constant through any changes of Vdd and resistor changes Vgs>Vt to turn on, if less than, it is called cutoff region Vth>0 1/2 un cox wl(Vgs-Vt)Vds
time interval of discharge for capacitor in parallel with half wave rectifier load
Vp = DC peak voltage(from RMS)
ripple voltage equation for half wave vs full wave rectifier REVIEW
Vp = peak voltage if non ideal Vp = Vp-Vd Vp is the peak voltage over the load so if nonideal diode, subtract the diode voltage
what is the ripple voltage?
Vr = peak to peak ripple voltage - range of the peak of when the diode turns off when capacitor is fully charged minus where the diode turns back on and the capacitor must start recharging when small Vr, you basically have DC voltage, approximatley equal to VP
Explain the voltage equations of a transformer and paramters of variables
Vs & Vp are in Vpk values! Vrms = Vpk/sqrt(2)
PIV of full wave rectifier
Vs-Vd0-(-vs) 2Vs - Vdo
what can we conclude from the small signal approximation?
Vt = .0259
what is the forward bias region current?
Vt = thermal voltage = kt/q = .0862T mV
what is the transformation of the zener diode? what is its use?
Vz0 = point at which the straight line of slope 1/rz interesect the voltages axis when information is given on the zener diode, it means by itself so you can zolve for Vz etc. Vz is the voltage over the whole thing, usually solve for Vz0 which is the voltage of just the source Iz>Izk, Iz = Izk when at the edge of the breakdown region used to protect circuit from higher voltages • If a microcontroller can only handle 0-5V, place a Zener Diode (about 4.6V) in the circuit. • If 10V is introduced into theterm-36 circuit, the Zener Diode will cause a breakdown and reduce the voltage to 4.6V. zener diodes have a reverse voltage breakdown, so if you apply a reverse bias at a certain voltage, allows current flow only up to a certain voltage zener diode breakdown voltage exceeded allows current to flow if voltage increases higher than the breakdown voltage, the voltage across the zener diode remains constant to the manufacteres voltage regulation providign constant dc output voltage in the face of changes in their load current and in system power supply voltage (THE VOLTAGE APPLIED TO EACH ZENER MUST BE GREATER THAN VZ FOR IT TO CONDUCT IN THE REVERSE BIAS) current can flow in the straight direction and it will have a regular voltage drop, however it is designed to operate in the other direction and when applied the right amount of voltage, it will hold that voltage forever (if zhener diode
Voltage drop over the diode alternative method
basically you can solve for I0 and then plug that in for ID in a later step
what happens to the channel when VDs increases (graphically)? NFET
channel width decreases on drain end and deepest on the source end
what must be taken into account when solving for a minium resistance given a source which changes voltages?
choose the voltage which iwill give you minimum current(the smallest) and the maximum current
what is enhancement vs depletion of a mosfet?
denoted by bold long line The depletion MOSFET has a physically implanted channel. Thus an n-channel depletion-type MOSFET has an n-type silicon region connecting the n+ source and the n+ drain regions at the top of the p-type substrate. Thus if a voltage vDS is applied between drain and source, a current iD flows for vGS=0. In other words, there is no need to induce a channel, unlike the case of the enhancement MOSFET. The channel depth and hence its conductivity can be controlled by vGS in exactly the same manner as in the enhancement-type device. Applying a positive vGS enhances the channel by attracting more electrons into it. Here, however, we also can apply a negative vGS, which causes electrons to be repelled from the channel, and thus the channel becomes shallower and its conductivity decreases. negative VGs depleted the channel, and depletion region is negative Vgs, where the greatest negative value of VGs is the threshold voltage The description above suggests (correctly) that a depletion-type MOSFET can be operated in the enhancement mode by applying a positive vGS and in the depletion mode by applying a negative vGS.
4 models of diodes
ideal diode battery plus diode battery plus resistance small signal
what are the three mosfet amplifier models? REVIEW!!!!!!!!!!!
if there is a resistor, it does not mean connected to ground there can be a voltage source which shorts out which connects the source straight to ground in the small signal approximation which will make it a common source mosfet amplifieer - if resistor on both, it is common source with Rs
explain each step of the small signal approximation graphically if resistors are on drain side
if theree was a resistor at the bottom on the source, it would be included with the input gate resistances are coming as an rin if connected in current mirror mode, and source resistances are with rin
what is the characteristic equation of a diode? (video) what to remember about the voltage drop? REVIEW REVIEW
input voltage vs output voltage (usually voltage over diode to the end of the circuit), solve for output in terms of input, may have to find current and then graph for piecewise functions remember the output voltage of diode cannot exceed voltage drop over diode+voltage after if voltage goes negative on source, treat it still as +Vi, but only the negative portion of the source stays on review note example treat vi as a variable x, just in piecewise forms of it
what is a clamping circuit? why it called that? explain square wave !!Q! REVIEIW
it clamps v0 to 0 volts, and raises the voltage due to input of -6v, capacitor will charge to -6 V and diode will be on, conducting 0 V then the positive 4V of the source is applied and the 6 volts is in the same direction due to polarity, so diode acts as open circuit, and add up v0 = vi+Vc so basically input is negative creates a short positve means open circuit on other end, and add the charged capacitor basically does not allow voltage to pass to output the diode will only conduct when input is negative, so curent flows in opposite direction giving capacitor that polarity and charges to -6 V. when +4V occurs, diode does not allow current to flow and capacitor retaisn voltage since it cannot discharge due to low resistance
What are the current/voltage characteristics of a resistor?
it is a linear device for a semiconductor slab with thickness ts and width w, the Area A = ts * w// R = pL/a// o (conductivity) = 1/p
if given Vz for a zener diode, what does that mean?
it means that the voltage, when applied at least Vz, will be Vz for all time(oriented in reverse bias direction)
what does it mean if two mosfets are in series and their currents are equal?
it means the amount of current passing is the same through both
what is the peak voltage of the rectified output? REVIEW
maximum voltage over the output after taking out voltage drops over all diodes
if gate voltage is 0 vs a positive value vs a negative value, how does this affect outputs of transistors? nmos vs pmos
nmos requires positive gate voltage to turn on pmos requires negative gate voltage to turn on if gate is 0, output is usually 0 as well if opposites are applied, they are off
how do determine nodes and then do nodal analysis?
nodes - points between any two terminal devices (when current sources exist or are plentiful) select a reference node and label all other nodes ex - va, vb, vc, grounnd apply kcl at junction using our voltage variables to create equivalent expressions ex - if currents do go directly to ground, dont worry about subtracting voltages because you are subtracting from ground solve equations using rref, combine all v1s and v2, put in same column in a matrix, use rref of that matrux, amount of unknowns is amount of equations needed, the single values, move to other side of equation and set equal to, can leave as positvie label all currents as coming so they are positive, the first voltage the current cross is the first one, subtract it from the second, if you do it this way make sure to subtract from ground. put currents going into so they are all positive,
gain and output resistance of cmos inverter CATCH?
only if input ac source is applied to both gatesz both r0s still presnet though, just gms go away
correct way to find incremental voltage REVIEW
open circuit current sources shrot circuit voltage sources
how do you find the regulation voltage if the supply changes by a certain percentage?
or just change input voltage, finnd the amount it changes increasing and decreasing the voltage, and then divide// i think if you are trying to find the percent change you can just short out the voltage sources and open circuit current sources due to the superposistion principle
What is the PIV? explain if you want it high or low, review?
peak inverse voltage (largest voltage diode withstand without breakdown) = Vs which is the peak of vs or the source voltage peak vs is given in RMS The maximum reverse-bias voltage that a diode can withstand without "breaking down" is called the Peak Inverse Voltage, or PIV rating. In semiconductor diodes, peak reverse voltage or peak inverse voltage is the maximum voltage that a diode can withstand in the reverse direction without breaking down or avalanching.[1][2] If this voltage is exceeded the diode may be destroyed. Diodes must have a peak inverse voltage rating that is higher than the maximum voltage that will be applied to them in a given application. For rectifier applications, peak inverse voltage (PIV) or peak reverse voltage (PRV) is the maximum value of reverse voltage which occurs at the peak of the input cycle when the diode is reverse-biased.[3][4] The portion of the sinusoidal waveform which repeats or duplicates itself is known as the cycle. The part of the cycle above the horizontal axis is called the positive half-cycle, or alternation; the part of the cycle below the horizontal axis is called the negative alternation. With reference to the amplitude of the cycle, the peak inverse voltage is specified as the maximum negative value of the sine-wave within a cycle's negative alternation.
what is the build of a diode? what are the IV characteristics of the ideal diode? *REVIEW*
positive terminal = anode negative terminal = cathode (side with the line) V>0 ,i!=0 V<0, i = 0 with 0 voltage drop
what is the small signal approximation equivelent with and without channel length modulation?
r0 = 1/(lamdaID) ID as in regular DC current in saturation
explain small signal model approximation
rd = nVt/ID Vt = .0259 replace diode with resistance? assuming vdt<nVT ID = I0E^Vd/nVT good for when voltage source changes values in incremental quantities
what are the two resistances of each region? REVIEW!!!! everytime which casues each one?
rds vs ro Rds - the resistance of the channel in the mosfet (between the drain and source) for a small Vds in triode ro - occurs in saturation due to channel modulation effect as Vds increases, the channel pinch off point becomes further away from the drain twoards the source, narrowing the amount of electrons, acting like a resistor Va = 1/lamda
what does it mean if their is a constant voltage applied to gate for small signal?
replace with ro
How does a diode act under forward bias vs reverse bias?
reverse (negative voltage) - ideal diode would be off forward (positive voltage) - ideal diode would be turned on when voltage = 0, the current = 0
what does it mean if more voltage is applied to cathode of a diode than the annode even if they are both positve?
reverse bias and diode will open circuit - as long as it is higher potential on one side it is able to pass
what to remember about a voltage drop over a diode?
take the voltage drop into account a voltage drop over the diode means the battery plus diode method
how do you find the input resistance to a circuit?
test voltage to the small signal approximation if two resistors are connected to ground going in opposite direction on the gate, just say R1||R2 +Rgs in series with the generator
explain the half wave rectifier what is its PIV? REVIEW!!!
the diode only allows current to pass in one direction so thats why when voltage sign flips the voltage is 0 there is a delay in the rise due to Vs needing to be greater than Vdo, and then it starts (diode doesnt turn on for battery+diode model until voltage of battery is reached) v0 = 0 ---> vs<Vd v0 =vs-Vd ---> vs>=VD PIV = Vs (peak of input) https://www.slader.com/discussion/question/a-full-wave-rectifier-circuit-with-a/
what do you do if there is a voltage source after a diode? how does reverse bias work?
the voltage drop over the diode will always be the source + diode voltage drop and will not be turned on until that voltage is reached and will hold that voltage regardless of the input voltage you want greater voltage to be on annode than the cathode before it starts conducting this could mean also -4 on annode side and -5 on cathode side (still forward bias) so if there is a votlage drop on the diode, it will not begin conducting until that voltage drop is reached
how do you solve small signal equivelants? REVIEW
this basically puts all resistances on the drain side in parallel since they are all gonna be with respect to ground once you turn off all DC source voltage source = short circuits current sources = open circuits?
how does the current act when VDs increases for an NFET graphically? explain each region
triode : Vds <Vgs-Vt Satruation: Vds > Vgs - Vt saturation- current pinched off on the drain end
what do you need to remember about parallel voltage drops?
voltage drops in parallel are equal
