TEST 3 ECET 205
a transistor can be tested using a voltmeter to check back and front resistances of emitter base, collector base, and collector emitter
false
digital circuits are often called two-state circuits because their q point always remains in the active region
false
hard saturation of a transistor results when there is just enough base current to cut off the transistor.
false
most analog VOMs have a special forward current gain test function.
false
the operating point found on a load line is labeled C because this point is often called the cut-off point
false
the two basic kinds of transistor circuits are rectifying and oscillating
false
what is the term used to describe when there is more than enough base current to saturate a transistor.
hard saturation
Voltage divider bias produces a fixed value of emitter current that results in a stable operating point that is the _________ current gain
independent
The main advantage of an octocoupler is electrical _________ between input and output circuits
isolation
coupling capacitors between transistor stages appear as _____ circuits to dc voltage and currents.
open
a photo-transistor has more sensitivity to light that a(n) ____________
photodiode
a _________ transistor is used when the electronics equipment has a negative power supply
pnp
the operating point on the load line is labeled Q because this point is called the
quiescent point
when the collector current has increased to its maximum possible value it is said to be in ________
saturation
collector feedback is also called
self bias
Collector feedback bias is also called
self-bias
collector feedback bias is still sensitive to changes in current gain, but it is used because of its
simplicity
the two kinds of transistor circuits are amplifying and ________
switching
the schematic diagram of a pnp transistor shows
the emitter as an arrow pointing in
Emitter feedback and collector feedback are typically not adequate because
there is not enough negative feedback
while testing a transistor with an ohmmeter, a high reverse/forward resistance ratio for the emitter base and base collector junctions indicates
this transistor is good
A transistor goes into saturation when the collector current has increased to its maximum possible value
true
switching circuits are usually designed to operate at saturation and cutoff
true
with amplifying circuits, the q point must remain in the active region under all operating conditions
true
the intent of emitter feedback bias is to swamp out the _______ in current gain.
variations
the mostly widely used transistor biasing circuit is called _______ bias
voltage divider
with a pnp transistor the base emitter junction will be forward biased
when the emitter voltage is 0.7V above the base voltage
what occurs when the line voltage is changing polarity from positive to negative or vice versa?
zero crossings
Transistor replacement, collector current changes, or temperature changes can produce large changes in
Beta DC
The voltage between emitter and ground is called the _________ voltage
emitter
historically, the first attempt at stabilizing the operating point of a transistor circuit was to use
emitter feedback bias
to prevent meter loading, a voltmeter used to make transistor circuit voltage measurements should have an input impedance of __________ ohms
10 Mega
using a firm voltage divider means that the collector current will be approximately
10 percent lower than the stiff value
A firm voltage divider means that the collector current will be approximately 10 percent higher than the stiff value.
False
A well designed voltage divider bias circuit is one in which the voltage divider appears stiff to the output resistance of the collector
False
Emitter feedback bias uses a capacitor that provides positive feedback in attempt to stabilize the operating point.
False
Emitter feedback has always been very popular
False
Since voltage-divider bias is derived from emitter bias, the Q point varies with the changes in current gain.
False
Voltage Divider bias is really collector bias in disguise
False
a two supply emitter bias circuit typically used in transistor circuits is the most popular method of providing transistor bias.
False
Whenever possible a designer will configure a stiff voltage divider for base bias because it will produce a stable Q point.
True
collector feedback bias is also called self bias
True
By exposing a transistors collector junction to light a manufacturer can produce
a photo-transistor
amplifier that use emitter bias have Q points that
are immune to changes in current gain
establishing a fixed value of base current is a result of _________ bias
base
what should a trouble shooter do if the base, collector, and emitter voltages in a transistor circuit all measure 0 V?
check supply voltage and leads
The saturation point determines the maximum
collector current for the circuit
the ___________ point determines the maximum possible collector to emitter voltage
cutoff
___________ circuits use base bias and are designed to operate at saturation and cutoff.
digital
with ambiguous troubles, the troubleshooter very often must
disconnect one suspected component and test it
