Transistors and Amplifiers Quiz: Test Your Understanding of Semiconductor Devices and Amplifier Circuits

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The n-type regions in an npn bipolar junction transistor are

(a) collector and base
(b) collector and emitter
(c) base and emitter
(d) collector, base, and emitter
Answer: (b) collector and emitter

The n-region in a pnp transistor is the

(a) base
(b) collector
(c) emitter
(d) case
Answer: (c) emitter

For normal operation of an npn transistor, the base must be

(a) disconnected
(b) negative with respect to the emitter
(c) positive with respect to the emitter
(d) positive with respect to the collector
Answer: (c) positive with respect to the emitter

The three currents in a BJT are

(a) forward, reverse, and neutral
(b) drain, source, and gate
(c) alpha, beta, and sigma
(d) base, emitter, and collector
Answer: (d) base, emitter, and collector

Beta (β) is the ratio of

(a) collector current to emitter current
(b) collector current to base current
(c) emitter current to base current
(d) output voltage to input voltage
Answer: (b) collector current to base current

Alpha (α) is the ratio of

(a) collector current to emitter current
(b) collector current to base current
(c) emitter current to base current
(d) output voltage to input voltage
Answer: (a) collector current to emitter current

If the beta of a certain transistor operating in the linear region is 30 and the base current is 1 mA, the collector current is

(a) 0.033 mA
(b) 1 mA
(c) 30 mA
(d) unknown
Answer: (c) 30 mA

If the base current of a transistor operating in the linear region increases,

(a) the collector current increases and the emitter current decreases
(b) the collector current decreases and the emitter current decreases
(c) the collector current increases and the emitter current does not change
(d) the collector current increases and the emitter current increases
Answer: (d) the collector current increases and the emitter current increases

When an n-channel JFET is biased for conduction, the gate is

(a) positive with respect to the source
(b) negative with respect to the source
(c) positive with respect to the drain
(d) at the same voltage as the drain
Answer: (b) negative with respect to the source

When the gate-to-source voltage of an n-channel JFET is increased, the drain current

(a) decreases
(b) increases
(c) stays constant
(d) becomes zero
Answer: (a) decreases

When a negative gate-to-source voltage is applied to an n-channel MOSFET, it operates in the

(a) cutoff state
(b) saturated state
(c) enhancement mode
(d) depletion mode
Answer: (d) depletion mode

In a common-emitter (CE) amplifier, the capacitor from emitter to ground is called the

(a) coupling capacitor
(b) decoupling capacitor
(c) bypass capacitor
(d) tuning capacitor
Answer: (c) bypass capacitor

If the capacitor from emitter to ground in a CE amplifier is removed, the voltage gain

(a) increases
(b) decreases
(c) is not affected
(d) becomes erratic
Answer: (b) decreases

When the collector resistor in a CE amplifier is increased in value, the voltage gain

(a) increases
(b) decreases
(c) is not affected
(d) becomes erratic
Answer: (a) increases

The output signal of a CE amplifier is always

(a) in phase with the input signal
(b) out of phase with the input signal
(c) larger than the input signal
(d) equal to the input signal
Answer: (b) out of phase with the input signal

The output signal of a common-collector amplifier is always

(a) in phase with the input signal
(b) out of phase with the input signal
(c) larger than the input signal
(d) exactly equal to the input signal
Answer: (a) in phase with the input signal

In a class A amplifier, the output signal is

(a) distorted
(b) clipped
(c) the same shape as the input
(d) smaller in amplitude than the input
Answer: (c) the same shape as the input

A class A amplifier conducts for

(a) 90° of input cycle
(b) 180° of input cycle
(c) 270° of input cycle
(d) 360° of input cycle
Answer: (d) 360° of input cycle

A class B amplifier conducts for

(a) 90° of input cycle
(b) 180° of input cycle
(c) 270° of input cycle
(d) 360° of input cycle
Answer: (b) 180° of input cycle

Feedback oscillators operate on the principle of

(a) signal feedthrough
(b) positive feedback
(c) negative feedback
(d) attenuation
Answer: (b) positive feedback

Which characteristic does not necessarily apply to an op-amp:

(a) high gain
(b) low power
(c) high input resistance
(d) low output resistance
Answer: (b) low power

In selecting an op-amp, suppose you have several choices. Of the CMRR values listed, the most desirable is

(a) 10 dB
(b) 20 dB
(c) 50 dB
(d) 100 dB
Answer: (d) 100 dB

The output voltage of a particular op-amp increases 8 V in 12 ms in response to a step voltage on the input. The slew rate is

(a) 0.667 V/ms
(b) 1.5 V/ms
(c) 96 V/ms
(d) 0.75 V/ms
Answer: (b) 1.5 V/ms

A noninverting op-amp configuration has an Ri of 1.0 kΩ and an Rf of 100 kΩ. If Vout is 5 V, the value of Vf is

(a) 50 mV
(b) 49.5 mV
(c) 495 mV
(d) 500 mV
Answer: (b) 49.5 mV

In the amplifier described in Question 4, the value of B is

(a) 0.01
(b) 0.1
(c) 0.0099
(d) 101
Answer: (a) 0.01

The closed-loop gain of the amplifier in Question 4 is

(a) 0.0099
(b) 1
(c) 99
(d) 101
Answer: (d) 101

One characteristic of a voltage-follower is

(a) Acl ≠ 1
(b) inversion
(c) high Rout
(d) noninversion
Answer: (a) Acl ≠ 1

An inverting amplifier has the following circuit values: Rf = 220 kΩ, Ri = 2.2 kΩ, and Aol = 25,000. The closed-loop gain is

(a) -100
(b) -0.01
(c) 100
(d) -250
Answer: (a) -100

If you know an op-amp’s open-loop gain and nothing else, you can determine the closed-loop gain of

(a) an inverting amplifier
(b) a noninverting amplifier
(c) a voltage-follower
(d) none of the amplifier configurations without additional information
Answer: (d) none of the amplifier configurations without additional information

The feedback attenuation of a voltage-follower is

(a) unity
(b) less than unity
(c) greater than unity
(d) variable
Answer: (a) unity

The value of B in a certain noninverting amplifier is 0.025. The closed-loop gain is

(a) unity
(b) 40
(c) 0.025
(d) undeterminable
Answer: (a) unity

The highest possible input resistance is achieved with the

(a) inverting amplifier
(b) noninverting amplifier
(c) differential amplifier
(d) voltage-follower
Answer: (d) voltage-follower

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