Feedback:
The process of
injecting a fraction of output energy of some device back to the input is known
as feedback. The gain with feedback is called closed loop gain. The gain without feedback is sometimes called open loop gain.
Feedback is a crucial concept in the world of electronics, and understanding the different types and classifications of feedback can be instrumental in designing high-performance circuits. In this blog post, we will explore the different types of feedback and their applications in electronic circuits.
Types of Feedback:
Feedback can be classified based on the nature of the feedback, electrical quantities of feedback, and circuit arrangement.
Based on the
nature of the feedback, feedback can be classified into two types:
- Positive feedback: When the feedback energy is in phase with the input signal, it is called positive feedback. Positive feedback increases the gain of the amplifier. That is why, sometimes it is also called ‘regenerative/direct’ feedback. However it has the disadvantages of increased distortion and instability. Therefore, positive feedback is seldom employed in amplifiers. One important use of positive feedback is in oscillators. If positive feedback is sufficiently large, it leads to oscillation.
- Negative feedback: When the feedback energy is out of phase with the input signal, it is called negative feedback. Negative feedback reduces the gain of the amplifier. That is why, it is sometimes called degenerative or inverse feedback. However, the advantages of negative feedback are:
1.Higher input impedance
2. Lower output impedance
3. Better stabilized gain
4. Reduction of noise
5. Improved frequency
response
6. More linear operation
Based on electrical quantities of feedback, it can be
classified into two types:
- Voltage feedback: When the feedback is proportional to the output voltage, it is known as voltage feedback.
- Current feedback: When the feedback is proportional to the output current, it is known as current feedback.
These types of feedback are commonly used in operational amplifiers and other electronic circuits to control gain and stability.
Based on the circuit arrangement, feedback can be classified into
four types:
- Voltage series feedback: Voltage series feedback occurs when the feedback signal is applied in series with the input signal.
- Current series feedback: Current series feedback occurs when the feedback signal is applied in series with the output current.
- Voltage shunt feedback: Voltage shunt feedback occurs when the feedback signal is applied in parallel with the input signal.
- Current shunt feedback: Current shunt feedback occurs when the feedback signal is applied in parallel with the output current.
Each type of feedback has its advantages and disadvantages, and the selection of the appropriate feedback type depends on the specific requirements of the circuit.
 |
| Fig: (i)Voltage series Feedback (ii) Current series Feedback (iii) Voltage shunt Feedback (iv) Current shunt Feedback |
Feedback is a crucial concept in the world of electronics, and understanding the different types and classifications of feedback can be instrumental in designing high-performance circuits. By selecting the appropriate type of feedback for a specific application, designers and engineers can create circuits that are stable, reliable, and perform optimally.