True or False 1. The following statements refer to the high frequency response o

Question

True or False

1. The following statements refer to the high frequency response of electronic amplifiers:

_ a) Adding AC emitter resistance to a CE amplifier provides greater bandwidth, DC bias stability, and input
resistance.
_ b) The Q point has very little effect on an amplifier's frequency response.
_ c) The FET common-source amplifier's BW is limited by the Miller effect which multiplies the feedback
capacitor (Cgd) to form a dominant time constant at the input side.
_ d) The CMRR of a differential amplifier initially falls off at high frequencies because of a falloff in the
differential-mode gain.
_ e) The cascode (CE-CB) amplifier has about the same voltage gain as the CE amplifier, but the cascode's
bandwidth is much higher because the Miller capacitor of the CE transistor in the transistor pair is small.
_ t) The phase of an amplifier with one zero and four poles will ultimately reach -270°.
_ g) Open circuit time constants can be used to reasonably estimate a circuit's lower frequency response, fL'
_ h) The Miller theorem cannot be readily used to estimate the upper -3dB frequency (fH) of a differential
amplifier's Common-Mode half circuit.

2. The effects of negative feedback on an amplifier:

_ a) It will always increase an amplifier's input resistance.
_ b) Amplifier's nonlinear distortion can be considerably reduced.
_ c) It will desensitize the gain of a closed loop amp.
_ d) It will always increase an amplifier's bandwidth.
_ e) It cannot reduce the noise or interference in an amplifier that originates outside the feedback loop.
_ t) Using series-series negative feedback will make the feedback amplifier behave more like an ideal
transresistance amp.
_ g) Using shunt-series negative feedback will make the feedback amplifier behave more like an ideal current
amp.

3. The following statements refer to output stages

_ a) A Class B power amplifier is operating at 50% of rated maximum power output to the load, and the power
transistors' metal cases measure 95 degrees. When the input signal increases to full output power, the
temperatures of the transistor cases become cooler.
_ b) Among the various choices for an output stage, class A type is the most widely used due to its linearity and
low standby power consumption.
_ c) For greater power output, compound PNP transistors can be used in a Class AB complementary push-pull
output stage.
_ d) The main application of a "VBE multiplier" is to increase the beta of lateral PNP transistors.
_ e) Except for the small amount of standby power dissipation, the efficiency of a Class AB output stage is
comparable to that of a Class B stage.
_ t) A Darlington compound NPN transistor has an overall beta of approximatelly (beta)^2.

Explanation / Answer

Answers:

a.) True --> Adding AC emitter resistance to a CE amplifier provides greater bandwidth, DC bias stability, and input
resistance.

b.) false--> Q point is inversely proportional to BW, higher the Q better is selectivity and vice versa

c.)True -->The FET common-source amplifier's BW is limited by the Miller effect which multiplies the feedback
capacitor (Cgd) to form a dominant time constant at the input side.

d.) False -->The CMRR of a differential amplifier initially falls off at high frequencies because of a falloff in the
differential-mode gain

e) True-->The cascode (CE-CB) amplifier has about the same voltage gain as the CE amplifier, but the cascode's
bandwidth is much higher because the Miller capacitor of the CE transistor in the transistor pair is small.
t) False--> The phase of an amplifier with one zero and four poles will ultimately reach -270°.
g) False--> Open circuit time constants can be used to reasonably estimate a circuit's lower frequency response, fL'
h)False--> The Miller theorem cannot be readily used to estimate the upper -3dB frequency (fH) of a differential
amplifier's Common-Mode half circuit.

2. The effects of negative feedback on an amplifier:

a) False-:> It will always increase an amplifier's input resistance.
b) True-->Amplifier's nonlinear distortion can be considerably reduced.
c)True--> It will desensitize the gain of a closed loop amp.
d) True-->It will always increase an amplifier's bandwidth

e.)False-->It cannot reduce the noise or interference in an amplifier that originates outside the feedback loop.
t) False--> Using series-series negative feedback will make the feedback amplifier behave more like an ideal
transresistance amp.
g)True-->Using shunt-series negative feedback will make the feedback amplifier behave more like an ideal current
amp.

3. The following statements refer to output stages

a) False-->A Class B power amplifier is operating at 50% of rated maximum power output to the load, and the power
transistors' metal cases measure 95 degrees. When the input signal increases to full output power, the
temperatures of the transistor cases become cooler.

b)False--> Among the various choices for an output stage, class A type is the most widely used due to its linearity and low standby power consumption.

c) False--> For greater power output, compound PNP transistors can be used in a Class AB complementary push-pull output stage.
d) False-->The main application of a "VBE multiplier" is to increase the beta of lateral PNP transistors.
e) True-->Except for the small amount of standby power dissipation, the efficiency of a Class AB output stage is comparable to that of a Class B stage.
t) True-->A Darlington compound NPN transistor has an overall beta of approximatelly (beta)^2.

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