PPT: Feedback Amplifier | Analog and Digital Electronics - Electrical Engineering (EE) PDF Download

 Page 1


FEEDBACK AMPLIFIER
Page 2


FEEDBACK AMPLIFIER
Contents:
? Introduction
? Conceptual Development Through Block Diagrams
? Properties of Negative Feedback
? Calculations of Open-Loop Gain, Closed-Loop Gain and Feedback
Factors
? T opologies of the Feedback Amplifier
? Effect of Feedback on Gain, Input and Output Impedances
? Practical Implementation of the Feedback T opologies
? Sensitivity
? Bandwidth Stability
? Effect of Positive Feedback
Page 3


FEEDBACK AMPLIFIER
Contents:
? Introduction
? Conceptual Development Through Block Diagrams
? Properties of Negative Feedback
? Calculations of Open-Loop Gain, Closed-Loop Gain and Feedback
Factors
? T opologies of the Feedback Amplifier
? Effect of Feedback on Gain, Input and Output Impedances
? Practical Implementation of the Feedback T opologies
? Sensitivity
? Bandwidth Stability
? Effect of Positive Feedback
Objectives
? In this chapter we will address the concept of feedback. Feedback is the
fundamental concept in the design of a stable amplifier and an unstable
oscillator circuit.
? Beginning with the conceptual development of feedback through block
diagrams, this chapter explains both negative and positive feedback, and
their effects on different circuit parameters.
? Calculations of open-loop gain and closed-loop gain have been done in
detail, followed by a discussion on the effects of feedback on gain, input
and output impedances.
? An overview of the practical implementation of feedback topologies,
and the sensitivity and bandwidth stability of the feedback amplifier has
also been provided.
? The chapter ends with an examination of the effects of  positive
feedback with emphasis on the Nyquist and Barkhausen criteria.
Page 4


FEEDBACK AMPLIFIER
Contents:
? Introduction
? Conceptual Development Through Block Diagrams
? Properties of Negative Feedback
? Calculations of Open-Loop Gain, Closed-Loop Gain and Feedback
Factors
? T opologies of the Feedback Amplifier
? Effect of Feedback on Gain, Input and Output Impedances
? Practical Implementation of the Feedback T opologies
? Sensitivity
? Bandwidth Stability
? Effect of Positive Feedback
Objectives
? In this chapter we will address the concept of feedback. Feedback is the
fundamental concept in the design of a stable amplifier and an unstable
oscillator circuit.
? Beginning with the conceptual development of feedback through block
diagrams, this chapter explains both negative and positive feedback, and
their effects on different circuit parameters.
? Calculations of open-loop gain and closed-loop gain have been done in
detail, followed by a discussion on the effects of feedback on gain, input
and output impedances.
? An overview of the practical implementation of feedback topologies,
and the sensitivity and bandwidth stability of the feedback amplifier has
also been provided.
? The chapter ends with an examination of the effects of  positive
feedback with emphasis on the Nyquist and Barkhausen criteria.
INTRODUCTION
? Feedback is one of the fundamental processes in
electronics. It is defined as the process whereby a portion
of the output signal is fed to the input signal in order to
form a part of the system-output control.
? Feedback is used to make the operating point of a transistor
insensitive to both manufacturing variations in as well as
temperature.
? There is another type of feedback called positive or
regenerative feedback in which the overall gain of the
amplifier is increased. Positive feedback is useful in
oscillators and while establishing the two stable states of
flip-flop.
Page 5


FEEDBACK AMPLIFIER
Contents:
? Introduction
? Conceptual Development Through Block Diagrams
? Properties of Negative Feedback
? Calculations of Open-Loop Gain, Closed-Loop Gain and Feedback
Factors
? T opologies of the Feedback Amplifier
? Effect of Feedback on Gain, Input and Output Impedances
? Practical Implementation of the Feedback T opologies
? Sensitivity
? Bandwidth Stability
? Effect of Positive Feedback
Objectives
? In this chapter we will address the concept of feedback. Feedback is the
fundamental concept in the design of a stable amplifier and an unstable
oscillator circuit.
? Beginning with the conceptual development of feedback through block
diagrams, this chapter explains both negative and positive feedback, and
their effects on different circuit parameters.
? Calculations of open-loop gain and closed-loop gain have been done in
detail, followed by a discussion on the effects of feedback on gain, input
and output impedances.
? An overview of the practical implementation of feedback topologies,
and the sensitivity and bandwidth stability of the feedback amplifier has
also been provided.
? The chapter ends with an examination of the effects of  positive
feedback with emphasis on the Nyquist and Barkhausen criteria.
INTRODUCTION
? Feedback is one of the fundamental processes in
electronics. It is defined as the process whereby a portion
of the output signal is fed to the input signal in order to
form a part of the system-output control.
? Feedback is used to make the operating point of a transistor
insensitive to both manufacturing variations in as well as
temperature.
? There is another type of feedback called positive or
regenerative feedback in which the overall gain of the
amplifier is increased. Positive feedback is useful in
oscillators and while establishing the two stable states of
flip-flop.
Advantage of Feedback  System:
? The feedback system has many advantages especially in
the control of impedance levels, bandwidth
improvement, and in rendering the circuit performance
relatively insensitive to manufacturing as well as to
environmental changes.
? These are the advantages of negative or degenerative
feedback in which the signal feedback from output to
input is 180 out of phase with the applied excitation. It
increases bandwidth and input impedance, and lowers
the output impedance.