Question 1

In a self- biased common- source amplifier, what purpose does resistor RG serve?
A)Keeps the gate at approximately zero volts
B)Develops the gate- source bias current
C)Prevents loading of the ac signal source
D)Both A and C above.

Accepted Answer

Resistor RG in a self-biased common-source amplifier helps to keep the gate at approximately zero volts, ensuring the gate-source voltage is set by other means (like a voltage divider or a source resistor), and it also prevents loading of the AC signal source, ensuring that the signal source does not have to drive a low impedance at the gate.

Question 2

-Refer to the figure above. If ID = 6 mA, the value of VGS is
A)- 19.8 V.
B)- 10.2 V.
C)9 V.
D)- 9 V.

Accepted Answer

D

Question 3

A CS amplifier has a voltage gain of 
A) gmRd.

B) $ \frac{g m R d}{(1+g m R d)} $.

C) $ \frac{\operatorname{gm} K_{5}}{(1+g m R d)} . $

D) gmRs.

Accepted Answer

The voltage gain of a common-source (CS) amplifier is given by the product of the transconductance (gm) and the drain resistance (Rd), which is gmRd. This is a fundamental characteristic of CS amplifiers in electronics.

Question 4

The ac equivalent circuit of a FET amplifier assumes that the capacitors A)have an X_C of 600 ▲ at the signal frequency. B)are treated like opens. C)have an X_Cof 1 M▲ at the signal frequency. D)are treated like shorts.

Accepted Answer

In the AC equivalent circuit of a FET amplifier, capacitors are treated like shorts because at signal frequency, they offer very low impedance, allowing AC signals to pass through them as if they were not present. This simplifies the analysis of the circuit's behavior with AC signals.

Question 5

-Refer to the figure above. If R3 opened, Vout would
A)increase.
B)decrease.
C)remain the same.
D)distort.

Accepted Answer

The answer of 
-Refer to the figure above. If R3...

Question 6

-Refer to the figure above. If C5 opened, the signal voltage across R7 would
A)increase.
B)be zero.
C)remain the same.
D)distort.

Accepted Answer

If C5 opened, it would break the circuit path for the signal, effectively isolating R7 from the rest of the circuit. This would result in no current flow through R7, and thus, the voltage across it would be zero.

Question 7

-Refer to the figure above. If R7 were to increase in value, Vout would
A)increase.
B)decrease.
C)remain the same.
D)distort.

Accepted Answer

Increasing R7 would increase the total resistance in the circuit, which would lead to an increase in Vout if the circuit is a voltage divider or similar configuration.

Question 8

Two FET amplifiers operated in cascade have gains of 6 dB and 8 dB. The total overall gain in dB is
A)64 dB.
B)14 dB.
C)2 dB.
D)48 dB.

Accepted Answer

The total overall gain in dB for cascaded amplifiers is the sum of the individual gains, so 6 dB + 8 dB = 14 dB.

Question 9

Which of the following is not a FET amplifier?
A)Emitter- follower
B)Common- drain
C)Source- follower
D)Common- gate

Accepted Answer

Emitter-follower is a type of bipolar junction transistor (BJT) amplifier configuration, not a field-effect transistor (FET) amplifier. The other options (B, C, D) are configurations of FET amplifiers.

Question 10

If the interstage coupling capacitor opens in a two stage FET amplifier, the output signal will
A)double in amplitude.
B)be slightly increased.
C)be slightly decreased.
D)be zero.

Accepted Answer

If the interstage coupling capacitor opens in a two-stage FET amplifier, it breaks the signal path between the stages, resulting in no signal being passed to the output, hence the output signal will be zero.

Question 11

-Refer to the figure above. If R1 opened, Vout would
A)increase.
B)decrease.
C)remain the same.
D)distort.

Accepted Answer

If R1 opened, the circuit would lose a path for current, but since Vout is determined by the voltage across R2 in a series circuit, and the total voltage from the source would still be applied across the series combination of R2 and the open circuit (where R1 was), Vout across R2 would remain the same.

Question 12

The capacitor connected to the source of a common source amplifier
A)is used for input coupling.
B)makes the source an ac ground point.
C)is needed for extra power supply filtering.
D)is used for output coupling.

Accepted Answer

In a common source amplifier, the capacitor connected to the source is used to make the source an AC ground point, allowing AC signals to pass while blocking DC.

Question 13

The main reason that the input resistance of FET amplifiers is so high is that the
A)gate junction is reverse- biased.
B)power supplies used are high voltage/low current.
C)biasing resistors are extremely small.
D)FET junctions are forward- biased and made of germanium.

Accepted Answer

The gate junction in FET (Field Effect Transistor) amplifiers is reverse-biased, which leads to a very small gate current. This results in a high input impedance or resistance, making one of the key advantages of FETs their high input resistance compared to bipolar junction transistors (BJTs).

Question 14

Which of the following is not an application of an analog MOSFET switch?
A)Switched capacitor circuit
B)Sample- and- hold circuit
C)Inverter
D)Analog multiplexer

Accepted Answer

Analog MOSFET switches are commonly used in applications that require the processing of analog signals, such as switched capacitor circuits, sample-and-hold circuits, and analog multiplexers. An inverter, on the other hand, is a digital logic circuit that is not typically considered an application of an analog MOSFET switch.

Question 15

-Refer to the figure above. Assuming midpoint biasing, if VGS = - 4 V, the value of RS that will provide this value is
A)1.2 k▲.
B)800 ▲.
C)80 ▲.
D)600 ▲.

Accepted Answer

The answer of 
-Refer to the figure above. Assuming midpoint...

Question 16

Which of the following is not a characteristic of a JFET- based cascode amplifier?
A)High input resistance
B)High frequency response
C)High gain
D)High input capacitance

Accepted Answer

JFET-based cascode amplifiers are known for their high input resistance, high frequency response, and high gain. However, they do not inherently have high input capacitance; in fact, one of the advantages of using a JFET is typically its low input capacitance, which contributes to the high frequency performance.

Question 17

When the input signal is large, a source follower has
A)a small distortion.
B)a voltage gain of less than one.
C)a high input resistance.
D)All of the above.

Accepted Answer

A source follower, by design, has a voltage gain slightly less than one due to the voltage drop across the source-gate junction, inherently possesses a high input resistance because the input is applied to the gate of a MOSFET or the base of a BJT, both of which draw minimal current, and typically exhibits small distortion for large input signals as it operates in the linear region of the transistor's characteristics.

Question 18

-Refer to the figure above. If ID = 4 mA, IDSS = 16 mA, and VGSoff)= - 8 V, VDS would be
A)10.8 V.
B)19.2 V.
C)30 V.
D)- 6 V.

Accepted Answer

The drain current ID is given by the equation ID = IDSS(1 - VGS/VGSoff)^2. Solving for VGS when ID = 4 mA, IDSS = 16 mA, and VGSoff = -8 V, we find VGS = -4 V. Using the Shockley's equation for JFETs, VDS can be calculated using the given parameters and the supply voltage, which results in VDS = 10.8 V.

Question 19

Changing ______can control the voltage gain of a common- source amplifier.
A)VDD
B)gm
C)RS
D)the input voltage

Accepted Answer

gm is the transconductance of the transistor, which is a measure of its ability to amplify a signal. By changing the gm, the voltage gain of the amplifier can be controlled.

Question 20

Which of the following is not part of a class D amplifier?
A)Switching amplifier
B)Low- pass filter
C)Oscillator
D)Pulse- width modulator

Accepted Answer

Class D amplifiers, also known as switching amplifiers, utilize pulse-width modulation (PWM), a low-pass filter, and switching techniques to amplify signals. An oscillator is not a necessary component of a class D amplifier; instead, the PWM signal, which is essential for the operation of a class D amplifier, is generated by a pulse-width modulator.

Quiz 9: Fet Amplifiers and Switching Circuits

In a self- biased common- source amplifier, what purpose does resistor RG serve?

-Refer to the figure above. If ID = 6 mA, the value of VGS is

A CS amplifier has a voltage gain of

The ac equivalent circuit of a FET amplifier assumes that the capacitors

-Refer to the figure above. If R3 opened, Vout would

-Refer to the figure above. If C5 opened, the signal voltage across R7 would

-Refer to the figure above. If R7 were to increase in value, Vout would

Two FET amplifiers operated in cascade have gains of 6 dB and 8 dB. The total overall gain in dB is

Which of the following is not a FET amplifier?

If the interstage coupling capacitor opens in a two stage FET amplifier, the output signal will

-Refer to the figure above. If R1 opened, Vout would

The capacitor connected to the source of a common source amplifier

The main reason that the input resistance of FET amplifiers is so high is that the

Which of the following is not an application of an analog MOSFET switch?

-Refer to the figure above. Assuming midpoint biasing, if VGS = - 4 V, the value of RS that will provide this value is

Which of the following is not a characteristic of a JFET- based cascode amplifier?

When the input signal is large, a source follower has

-Refer to the figure above. If ID = 4 mA, IDSS = 16 mA, and VGSoff) = - 8 V, VDS would be

Changing ______can control the voltage gain of a common- source amplifier.

Which of the following is not part of a class D amplifier?