ELEC 2 Q AND A
recall what a capacitor is capable?
A capacitor is capable of storing electrical charge and electrical energy.
How many states does a monostable circuit have?
A monostable circuit has one stable output state and one unstable output state.
What is a shift register?
A shift register is a device that enables data to be passed from one flip-flop to the next, on each successive clock pulse.
How many states does the astable circuit have?
An astable circuit has no stable output states but continually changes from one state to another.
sketch graphs of voltage against time for a capacitor charging and discharging
Charging capacitor on the left. Dis-charging capacitor on the right.
describe the use of feedback to make a rising edge triggered D-type flip-flop divide by 2;
D is connected to NOT Q. SET and RESET are low. Input to the clock. This can also be used as a frequency divider. It divides the frequency by two, The output of this circuit is high for 50% of the time and low for 50% of the time. This is a 1:1 mark space ratio
recall the circuit diagram of a bistable latch based on NAND gates and describe its operation and function;
If the Set pin is momentarily made zero, one or more times, Q will go high and stay high. If the Reset pin is momentarily made zero, one or more times, Q will go low and stay low. The first SET pulse changes the state of the BISTABLE. Subsequent SET pulses have no effect. The first RESET pulse changes the state of the BISTABLE. Subsequent RESET pulses have no effect. Function is a one bit memory circuit.
describe the operation of an astable based on a 555 timer;
If the output is high, the discharge transistor is off. C1 charges towards Vs through Ra and Rb until the threshold rises above 2/3 of the supply voltage. The output goes low and the discharge transistor turns on. C1 discharges towards 0 Volts through Rb until the threshold drops below 1/3 of the supply voltage. The output goes high again and the steps above repeat.
recall how rising edge triggered D-type flip-flops can be used to form a shift register and describe its operation and applications.
On the rising edge of the clock pulse, each D is copied to the next Q and all the data moves one place to the right. The data moves one place to the right along the shift register. SET and RESET connected to each other and going to logic 0. All clocks connected to each other. Q connected to D and data input to first D.
What is the equation for time period of a monostable?
T = 1.1RC
explain the meaning of and calculate the value of the time constant for RC circuits;
The time constant for the circuit is the time taken to discharge to 37% of the initial voltage or to charge to 63% of the final voltage. T = RC
describe the operation of a monostable based on a 555 timer?
The timer starts when the trigger voltage drops below Vs / 3. The output goes high and the discharge transistor turns off. C charges through R towards Vs. When the voltage across C reaches 2/3 of Vs, the timer resets and the output goes low. The discharge transistor turns on and quickly discharges C to zero volts. Trigger pulses are ignored.
recall the symbol for a rising edge triggered D-type flip-flop and describe its operation and function;
This is called edge triggered. If the DATA input changes between clock pulses, this has no effect on the output. The rising edge of the clock pulse stores the input bit so this flip flop can be used as a data latch (memory). A single D Type Flip Flop can store one bit. On the rising edge of the clock pulse, If D = 1 the circuit is "SET and Q goes high. If D = 0 the circuit is "RESET" and Q goes low.
recognise, draw and use the circuit diagram of a monostable based on a 555 timer circuit?
Threshold and discharge terminal connected. These two terminals connected to the resistor and capacitor. Resistor in series with capacitor. Resistor and input connected to trigger. Control connected to 0V via a capacitor. GND connected to 0V. RESET and Vs connected to high volt rail.
recognise, draw and use the circuit diagram of an astable based on a 555 timer circuit?
Trigger is connected to threshold. Both connected to the capacitor to resistor section. Resistor in series with another resistor and capacitor. Discharge terminal connected to the resistor to resistor section. Control connected to 0V via a capacitor. GND connected to 0V. RESET and Vs connected to high volt rail.
recall what a capacitor will block and allow?
a capacitor will block a direct current but will allow the passage of an alternating current;
recall what the voltage is after one time constant for a charging and dis-charging capacitor?
after one time constant: for a charging capacitor, V = 0.63Vs for a discharging capacitor, V = 0.37Vs, where Vs is the supply voltage and V is the voltage across the capacitor;
convert a 4-bit binary number to decimal or hexadecimal notation;
convert a 4-bit binary number to decimal or hexadecimal notation
describe the advantages of push-pull amplifier subsystems over single ended output subsystems;
describe the advantages of push-pull amplifier subsystems over single ended output subsystems;
describe the common types of distortion associated with push-pull amplifier subsystems (cross-over and saturation/clipping) and how they can be reduced;
describe the common types of distortion associated with push-pull amplifier subsystems (cross-over and saturation/clipping) and how they can be reduced;
design 4-bit modulo-N counters based on rising edge triggered D-type flip-flops, and draw timing diagrams for these counters;
design 4-bit modulo-N counters based on rising edge triggered D-type flip-flops, and draw timing diagrams for these counters
draw and recognise a summing op-amp amplifier circuit and describe its applications;
draw and recognise a summing op-amp amplifier circuit and describe its applications;
draw and recognise the enhancement mode MOSFET (both n- and p-channel) source follower amplifier circuits and describe their applications;
draw and recognise the enhancement mode MOSFET (both n- and p-channel) source follower amplifier circuits and describe their applications
draw and recognise the inverting op-amp amplifier circuit and describe its applications;
draw and recognise the inverting op-amp amplifier circuit and describe its applications
draw and recognise the non-inverting op-amp amplifier circuit and describe its applications;
draw and recognise the non-inverting op-amp amplifier circuit and describe its applications;
draw and recognise the push-pull amplifier circuit using p- and n-channel enhancement mode MOSFETs and describe its operation and applications;
draw and recognise the push-pull amplifier circuit using p- and n-channel enhancement mode MOSFETs and describe its operation and applications;
draw and recognise the single op-amp difference amplifier circuit and describe its applications;
draw and recognise the single op-amp difference amplifier circuit and describe its applications
draw and recognise the voltage follower op-amp amplifier circuit and describe its applications;
draw and recognise the voltage follower op-amp amplifier circuit and describe its applications;
estimate the maximum power output from a pushpull amplifier subsystem.
estimate the maximum power output from a pushpull amplifier subsystem.
estimate the power dissipated in a source follower and describe methods for removing the excess heat generated;
estimate the power dissipated in a source follower and describe methods for removing the excess heat generated;
What is the equation to work out frequency of an astable?
f = 1.44 / (RA+2RB)C
What factors would affect when choosing an appropriate capacitor?
maximum working voltage polarisation leakage current tolerance
recall and use the definition of bandwidth of an amplifier as the frequency range over which the power gain is within 50% of the maximum;
recall and use the definition of bandwidth of an amplifier as the frequency range over which the power gain is within 50% of the maximum;
recall and use the definition of bandwidth of an amplifier as the frequency range over which the voltage gain is within 70% of the maximum;
recall and use the definition of bandwidth of an amplifier as the frequency range over which the voltage gain is within 70% of the maximum
recall that for a real op-amp, the product of voltage gain and bandwidth is a constant;
recall that for a real op-amp, the product of voltage gain and bandwidth is a constant
recall that negative feedback is used to reduce the overall voltage gain of an op-amp amplifier subsystem.
recall that negative feedback is used to reduce the overall voltage gain of an op-amp amplifier subsystem.
recall that the input resistance is equal to that of the op-amp;
recall that the input resistance is equal to that of the op-amp
recall that the input resistance is equal to the resistance of the op-amp.
recall that the input resistance is equal to the resistance of the op-amp.
recall that the input resistance is equal to the value of the input resistor, and that the circuit has a virtual earth point;
recall that the input resistance is equal to the value of the input resistor, and that the circuit has a virtual earth point
recall that the input resistance of each input is different and comparatively low;
recall that the input resistance of each input is different and comparatively low
recall that the input resistance of each input is equal to the value of its input resistor, and that the circuit has a virtual earth point;
recall that the input resistance of each input is equal to the value of its input resistor, and that the circuit has a virtual earth point;
recall that the voltage gain of a voltage follower is 1, but that the current and power gain can be very large;
recall that the voltage gain of a voltage follower is 1, but that the current and power gain can be very large;
recall what the equation for the time constant is when the voltage is at 0V, half of the supply voltage or at the supply voltgae?
recall that: after 0.69RC, V = 0.5Vs after 5RC for a charging capacitor, V ≈ Vs after 5RC for a discharging capacitor, V ≈ 0
describe the use of a BCD or hexadecimal decoder with a seven segment display.
recall the properties of an ideal op-amp
What is the combined capacitance of capacitors connected in series and parallel combinations?
series: 1/CT = 1/C1 + 1/C2 parallel: CT = C1 + C2
What is the equation to work out time high for an astable?
tH = 0.7(RA+RB)C
What is the equation to work out time low for an astable?
tL = 0.7RBC
recall what the unit of capacitance is and what are practical capacitors usually measured in?
the unit of capacitance is the farad and that practical capacitors are usually measured in pF, nF and µF
use the formula Vout = (V+-V-) Rf R1
use the formula Vout = (V+-V-) Rf R1
use the formula Vout = - Rf Vin Rin
use the formula Vout = - Rf Vin Rin
use the formula Vout = -Rf V1 + V2 + V3 R1 R2 R3
use the formula Vout = -Rf V1 + V2 + V3 R1 R2 R3
use the formula Vout = 1+ Rf Vin Rin
use the formula Vout = 1+ Rf Vin Rin
use the formula power gain = Pout Pin
use the formula power gain = Pout Pin
use the formula voltage gain = Vout Vin
use the formula voltage gain = Vout/ Vin
