it's about amplifier

1. WELCOME
GROUP 5

2. • Safayet Hossain
Student of CSE dept of
Daffodil International University,Bangladesh

3. POSITIVE FEEDBACK AMPLIFIER

4. WHAT IS AN AMPLIFIER?
An amplifier is an electronic device that increases the voltage, current,
or power of a signal. Amplifiers are used in wireless communications
and broadcasting, and in audio equipment of all kinds. They can be
categorized as either weak-signal amplifiers or power amplifiers.

5. DEFINITION OF FEEDBACK
Feedback is defined as the process in which a part of output signal
(voltage or current) is returned back to the input.
In the feedback process a part of output is sampled and fed back to the
input. The fed back signal can be in phase with or out of phase with the
original input signal.
The amplifier that operates on the
principle
of feedback is known as feedback
amplifier.

6. • If the original input signal and the feedback signal are in
phase, the feedback is called as positive feedback.
• However if these two signals are out of phase then the
feedback is called as negative feedback.
TYPES OF FEEDBACK
1. Positive feedback
2. Negative feedback.

7. APPLICATIONS OF POSITIVE FEEDBACK
Positive feedback is used in oscillators where
an output of a frequency is needed. It is also
used to generate hysteresis in an amplifier,
which allows an amplifier to produce smooth
signals from noisy inputs.
Due to the controlled use of positive feedback,
sufficient amplification can be derived from a
single vacuum tube or valve (centre).

8. • Gain is reduced.
• Bandwidth is increased.
• Input impedance goes up. Output impedance goes
down. Distortion goes down.
• Signal to noise ration improves.
• Stability may be reduced, if the amplifier compensation
isn't correct.
APPLICATIONS OF POSITIVE FEEDBACK

9. ADVANTAGES OF POSITIVE FEEDBACK
AMPLIFIER
There are numerous advantages for Negative feedback amplifier over
positive feedback.
And having only one.
 The amplifier with positive feedback increases the overall Gain. While the
negative feedback amplifier reduces gain considerably.

10. 1. Very prone to oscillation.
2. Poor freq. response.
3. More distortion.
4. More drift.
DISADVANTAGES OF POSITIVE FEEDBACK
AMPLIFIER