Question

An oscillator is an amplifier with

• A. high gain
• B. no feedback
• C. negative feedback
• D. positive feedback

Hint:

Oscillators use positive feedback to generate continuous waveforms without input.

Answer 1

The Correct Option is D

An oscillator is essentially an amplifier that produces self-sustained oscillations without an external input signal. This is achieved by feeding a portion of the output back to the input in phase.
This is called positive feedback, and it ensures that oscillations are maintained.
- Negative feedback is used in amplifiers to stabilize gain.
- Positive feedback is required for oscillators to build and sustain the waveform.

Answer 2

Step 1: Understand the role of an oscillator
An oscillator is a device that generates a continuous periodic waveform without any input signal.

Step 2: Relation to amplifier
An oscillator can be thought of as an amplifier with feedback.
The amplifier amplifies the signal, and the feedback loop returns part of the output back to the input.

Step 3: Type of feedback needed
- Negative feedback reduces the gain and stabilizes the system.
- Positive feedback reinforces the input signal, which can sustain oscillations.

Step 4: Why positive feedback is necessary
For sustained oscillations, the feedback must be positive and of the right magnitude to compensate for losses.
This ensures the amplifier keeps generating a steady output signal without an external input.

Step 5: Final Conclusion
Therefore, an oscillator is an amplifier with positive feedback.