(a) Rectifier Circuit

• Converts AC (Alternating Current) into DC (Direct Current).
• Input: AC signal.
• Output: DC signal.
• Operation: Conducts during the positive half cycle of the input signal (half-wave rectifier) or during both half cycles (full-wave rectifier).
• Types: Half-wave, full-wave, bridge rectifier.
• Feedback: No feedback involved.
• Use Case: Used continuously for powering DC loads.

The sketch shows a simplified representation of an AC input waveform being converted into a pulsating DC waveform by a rectifier. A smoothing capacitor is added to reduce the pulsations and produce a more constant DC output.

(b) Amplifier Circuit

• Amplifies the amplitude of a weak signal without altering its waveform.
• Input: Weak signal to be amplified.
• Output: Amplified version of the input signal.
• Operation: Amplifies signals during both positive and negative cycles.
• Types: Categorized by frequency (audio, RF), or by physical placement (voltage, current amplifiers).
• Feedback: Uses negative feedback to stabilize gain.
• Use Case: Repeatedly used in circuits to maintain signal strength.

This sketch illustrates a generic amplifier. The input signal is smaller than the output signal.

(c) Oscillator Circuit

• Generates periodic, oscillating electronic signals such as sine waves or square waves.
• Input: DC supply.
• Output: AC signal.
• Operation: Converts DC into AC using positive feedback.
• Types: Linear (sine wave oscillators) and non-linear (square wave, sawtooth oscillators).
• Feedback: Uses positive feedback to sustain oscillations.
• Use Case: Used initially in circuits to provide a signal source.