2. feedback Concepts: Types Of Negative Feedback – Modification Of Gain,
Bandwidth, Input And Output Impedances, Applications.
Oscillators: RC Phase Shift, Wein Bridge, LC And Crystal Oscillators
(Qualitative Treatment Only).
UNIT-III FEEDBACK AMPLIFIERS & OSCILLATORS
MATRUSRI
ENGINEERING COLLEGE
3. MATRUSRI
ENGINEERING COLLEGE
INTRODUCTION
• Feedback plays an important role in electronic circuits where some
part of the output is fed back to the input through a feedback network.
So at the input side there is source and feedback signals.
• When the source signal is in phase with feedback signal, it is called as
positive feedback.
• When the source signal is out of phase with feedback signal, it is called
as negative feedback.
• Negative feedback employed in amplifying the signals and positive
feedback is employed in oscillator circuits.
• An oscillator is an electronic circuit which employs a positive feedback
where the source signal and feedback signal both are in phase.
• These oscillators are used to generate oscillations which can be sine or
triangular or rectangular waves.
11. MATRUSRI
ENGINEERING COLLEGE
Based on Sampling network and mixer, negative feedback amplifiers are
classified into
1) Voltage Series Feedback Amplifier
2) Voltage Shunt Feedback Amplifier
3) Current Series Feedback Amplifier
4) Current Shunt Feedback Amplifier
