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1. Feedback Amplifier
LAM GIA HUY – 20ED10103

2. TABLE OF CONTENTS
01 02 03 04
Overview about
Feedback Amplifier
Properties of
Negative
feedback
Kind of Negative
voltage and current
feedback
Effect of feedback and
Answer the question

3.  Feedback is one of the most basic electrical operations.
It is described as the process of feeding a portion of the
output signal to the input signal as part of the system-
output control.
 It is used to make a transistor's operating point
insensitive to both contructive and temperature
differences.
 Another sort of feedback is positive or negative
feedback, in which the amplifier's total gain is raise.In
oscillators and constructing the two stable states of a
flip-flop, positive feedback is important.
 ed.
1. Overview about Feedback
Amplifier

4. Types of Feedback
Amplifiers
 Positive Feedback Amplifier
The input signal, which might be a voltage signal, is increased by the
feedback supplied to it. A direct amplifier is another name for it. However,
these amplifiers are not very excellent at amplification, but they may be
utilised in a variety of oscillators.
 Negative Feedback Amplifier
 If the amplifier's input signal diminishes as a result of its application, the
feedback signal is applied. Voltage or current signals can be used as
input. A negative sort of feedback is what it's called. An inverse amplifier
is another name for it. The noise created in the circuit is decreased in
this scenario.

5. 2.PROPERTIES OF NEGATIVE
FEEDBACK:
 Negative feedback increases the input impedance of the
voltage amplifier.
 The output impedance of the voltage amplifier can be
further lowered by negative feedback.
 Negative feedback increases the frequency response and
the bandwidth of the amplifier.
 Negative feedback increases the linear range of operation
of the amplifier.
 Negative feedback causes reduction in noise.
 Phase distortion is reduced.

6. 3. Amplifiers Negative
Feedback
Negative Voltage Feedback
The voltage feedback to the amplifier's input is proportionate to
the output voltage in this manner. This is further divided into
two categories:
• Voltage-series feedback
• Voltage-shunt feedback
Negative Current Feedback
The voltage feedback to the amplifier's input is proportionate to
the output current in this manner. This is further divided into
two categories.
• Current-series feedback
• Current-shunt feedback

7. Voltage amplifiers with voltage-series
feedback:
 The algebraic sum of the input signal Vs and the feedback signal Vo, where
Vo is the output voltage, equals the basic amplifier's input voltage Vi.

8. Current-Series or Series-Series
Feedback:
 The output current Io of a trans-conductance feedback amplifier is
proportional to the input voltage Vs. The voltage Vf is the feedback signal,
which is added to Vs at the basic amplifier's input.

9. Current amplifiers with current-shunt
feedback
 The output current Io of the current-shunt feedback amplifier is proportional
to the input current Ii. As a result, it's a current amplifier.
 If the input current of the basic amplifier is Ii = Is + If and the output current is
Io = I L, the feedback signal is the current.

10. Voltage-Shunt or Shunt-Shunt
Feedback
 The voltage-shunt feedback amplifier, also known as a shunt-shunt feedback
amplifier, generates an output voltage Vo proportional to the input current Is.
The algebraic sum of Equals and the feedback current If is the basic
amplifier's input current Ii.

11. Table the amplifier properties that are
influenced by various forms of negative
feedback.

12. 4. EFFECT OF FEEDBACK ON GAIN,
INPUT AND OUTPUT IMPEDANCES:
The impact of
negative feedback on
an amplifier is
examined in terms of
gain, gain stability,
distortion, noise,
input/output
impedance,
bandwidth, and gain-
bandwidth product.

13. feedback oscillator require?
Why?
Phase with the input signal.Positive feedback improves
amplifier gain while simultaneously increasing distortion,
noise, and instability. Because of these drawbacks,
positive feedback is rarely used in amplifiers. Positive
feedback, on the other hand, is employed in oscillators.

14. What type of feedback does an
operational amplifier require? Why?
Negative feedback is achieved by linking the op-output
amp's voltage to the inverting input. It is the key to creating
a self-stabilizing system (this is true not only of op-amps,
but of any dynamic system in general).

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