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• 1. Amplifier Basics
• 2. Class A Amplifier Design
• 3. Multistage Amps & NFB
• 4. Amplifier Circuits
• 5. Power Amplifiers
• 6. Operational Amplifiers

Module 3.5

Negative Feedback Quiz

Try our quiz, based on the information you can find in Amplifiers Module 3. Submit your answers and see how many you get right. If you get any answers wrong. Just follow the hints to find the right answer and learn about Amplifiers as you go.

• a) More gain, wider bandwidth and reduced noise.
• b) Wider bandwidth, better stability and less distortion.
• c) Less noise, less distortion and predictable gain.
• d) Predictable gain, better reliability and wider bandwidth.

2.

If a voltage amplifier has an open loop gain (A_O) of 150 and a feedback factor (β) of 1/20, what will be the approximate gain with negative feedback applied?

• a) 18
• b) 55
• c) 36
• d) 70

3.

What is the NFB method being used in Fig. 3.5.1?

• a) Voltage derived, parallel fed.
• b) Voltage derived, series fed.
• c) Current derived, parallel fed.
• d) Current derived, series fed.

4.

What is the main advantage of using direct coupling in multi stage NFB amplifiers?

• a) It is more efficient than indirect coupling.
• b) It increases the input impedance of the amplifier.
• c) It reduces phase shifts.
• d) It allows more stages to be used.

5.

Refer to Fig. 3.5.2: Which of the following statements most accurately describes the type of inter stage coupling and method of feedback used?

• a) ) Direct coupling with DC negative feedback.
• b) ) Resistive coupling with AC negative feedback.
• c) Capacitive coupling with AC and DC negative feedback.
• d) DC coupling with AC and DC negative feedback.

6.

Refer to Fig. 3.5.2: Assuming that the input signal is normal, what would be the probable effect on the circuit if R4 became open circuit?

• a) No output signal.
• b) Normal output signal.
• c) Large and distorted output signal.
• d) Small and distorted output signal.

7.

To increase the input impedance, and reduce the output impedance of a multi stage amplifier, which of the following NFB methods should be used?

• a) Voltage derived, parallel fed.
• b) Current derived, parallel fed.
• c) Voltage derived, series fed.
• d) Current derived, series fed.

8.

In an audio amplifier using NFB which of the following methods would be most effective in reducing electro-magnetically induced noise from the power supply?

• a) Using a low pass filter in the negative feedback system.
• b) Decoupling the DC power lines using both electrolytic and polyester capacitors.
• c) Using a high pass filter in the negative feedback system.
• d) Using electromagnetic screening on the power supply components.

9.

Negative feedback loops avoid the use of reactive components where possible to minimise which of the following effects?

• a) Amplitude distortion.
• b) Phase distortion.
• c) Frequency distortion.
• d) External noise.

10.

The audio amplifier response curve illustrated in Fig. 3.5.3 shows which of the following problems?

• a) Frequency distortion.
• b) Phase distortion.
• c) Bandwidth distortion.
• d) Amplitude Distortion.

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