1. The main purpose of an amplifier is to:
A. Convert AC to DC
B. Amplify the amplitude of a signal
C. Convert low frequencies to high frequencies
D. Filter signals
Answer: B. Amplify the amplitude of a signal
2. The amplifier class that has the highest efficiency is:
A. Class A
B. Class B
C. Class AB
D. Class D
Answer: D. Class D
3. In an amplifier, the gain is defined as the ratio of:
A. Output signal to input signal
B. Input power to output power
C. Output power to input signal
D. Input voltage to output current
Answer: A. Output signal to input signal
4. The ideal gain of an amplifier is:
A. Zero
B. One
C. Infinite
D. 1000
Answer: C. Infinite
5. Which type of amplifier is typically used in audio systems to increase the volume of sound?
A. Power amplifier
B. Differential amplifier
C. Operational amplifier
D. Voltage amplifier
Answer: A. Power amplifier
6. In a class A amplifier, the output transistor conducts:
A. For half of the input signal
B. Continuously for the full cycle of the input signal
C. For a quarter of the input signal
D. Only for the positive half-cycle of the input
Answer: B. Continuously for the full cycle of the input signal
7. The main disadvantage of a class A amplifier is:
A. Low efficiency
B. High distortion
C. Low power gain
D. High efficiency
Answer: A. Low efficiency
8. A class B amplifier is characterized by:
A. Amplifying the entire input signal
B. Amplifying only the positive half of the input signal
C. Amplifying only the negative half of the input signal
D. Amplifying half of the input signal with two transistors, one for positive and one for negative half
Answer: D. Amplifying half of the input signal with two transistors, one for positive and one for negative half
9. Which of the following amplifiers is known for producing minimal crossover distortion?
A. Class A amplifier
B. Class B amplifier
C. Class AB amplifier
D. Class D amplifier
Answer: C. Class AB amplifier
10. A class D amplifier is often used in:
A. High-power audio amplification
B. Low-power applications
C. Digital signal processing
D. Both high-power audio and efficient power supplies
Answer: D. Both high-power audio and efficient power supplies
11. In a common-emitter amplifier, the input is applied to the:
A. Collector
B. Emitter
C. Base
D. Base and emitter
Answer: C. Base
12. In a common-collector amplifier (also called an emitter follower), the output is taken from the:
A. Base
B. Emitter
C. Collector
D. Ground
Answer: B. Emitter
13. A common-base amplifier has a voltage gain that is:
A. Greater than 1
B. Less than 1
C. Equal to 1
D. Zero
Answer: A. Greater than 1
14. The primary function of a differential amplifier is to:
A. Amplify the difference between two input signals
B. Amplify a single input signal
C. Amplify both input signals equally
D. Convert AC signals to DC
Answer: A. Amplify the difference between two input signals
15. In an op-amp based non-inverting amplifier, the input signal is applied to the:
A. Inverting input
B. Non-inverting input
C. Output terminal
D. Both inverting and non-inverting inputs
Answer: B. Non-inverting input
16. The primary application of an operational amplifier (op-amp) is in:
A. Oscillator circuits
B. Amplifying weak signals
C. Voltage regulation
D. Power supply design
Answer: B. Amplifying weak signals
17. Which of the following amplifiers is typically used in radio-frequency (RF) circuits?
A. Voltage amplifier
B. Power amplifier
C. Transistor amplifier
D. High-frequency amplifier
Answer: D. High-frequency amplifier
18. A low-noise amplifier (LNA) is used to:
A. Amplify high-frequency signals without significant noise
B. Reduce the noise of an audio signal
C. Increase power efficiency
D. Provide high-gain amplification in power circuits
Answer: A. Amplify high-frequency signals without significant noise
19. Which of the following is an application of a buffer amplifier?
A. Increasing the voltage of a signal
B. Matching impedances between circuits
C. Converting AC to DC
D. Decreasing the power output of a signal
Answer: B. Matching impedances between circuits
20. A power amplifier is used in applications requiring:
A. Voltage amplification
B. High-current output
C. Signal filtering
D. Low distortion
Answer: B. High-current output