Negative feedback vs Positive feedback | Difference between Negative feedback and Positive feedback
This page compares Negative feedback vs Positive feedback and mentions difference between Negative feedback and Positive feedback in amplifiers. It mentions advantages and disadvantages of negative feedback over positive feedback.
As we know feedback is process in which part or portion of output signal is fed back to input port. It is used to control dynamic behaviour of the circuit or system.
There are two types of feedback in amplifier.
• Positive feedback
• Negative feedback
If original input signal and feedback signal are in phase, the feedback type is known as positive feedback. It tends to increase the output.
If original input signal and feedback signal are out of phase, the feedback type is known as negative feedback. It tends to reduce the output.
Depending upon sampling type and mixing networks,
feedback amplifiers are categorized as follows.
• Voltage series feedback
• Current series feedback
• Current shunt feedback
• Voltage shunt feedback
| Parameter | Positive Feedback | Negative Feedback |
|---|---|---|
| Overall phase shift | 0 or 360 degrees | 180 degrees |
| Input and output voltage, noise | increases due to feedback | Decreases due to feedback |
| Feedback signal and input signal | In phase | Out of phase |
| Gain | increases | decreases |
| Stability | poor | better |
| applications or use | oscillators | amplifiers |
Advantages and disadvantages of negative feedback over positive feedback
Following are the advantages of negative feedback over positive feedback.
• Negative feedback stabilizes gain of amplifier.
• Input resistance increases for certain configurations.
• Output resistance decreases for certain configurations.
• Operating point is stabilized.
• The negative feedback is employed in various applications such as
electronic amoplifiers, regulated power suplies, wideband amplifiers etc.
Following are the disadvantages of negative feedback over positive feedback.
• Reduction in gain
• Reduction in input resistance in case of current shunt and voltage shunt type
amplifiers.
• Increase in output resistance in case of current series and current shunt feedback amplifiers.
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