What is the difference between negative and positive feedback?

Question

Thanks Jen but I'm speaking in scientific terms..

Answer 1

Positive feedback is something good like "This was a great story"

Negative feedback is something bad like. "I will never eat at this place again."

Answer 2

Much depends upon the system being regulated.

Negative feedback:

1. Tends to opposite excessive change (large amplitude) and wants to hold a system within a limited operating range.

2. In the case of an amplifier, it tends to reduce circuit gain and increase device operating bandwidth.

3. Tends to create system stability by ensuring linear operation.

Positive feedback:

1. Tends to generate excessive system gain, noise, narrows bandwidth, and can cause oscillation.

2. Creates instability and tends to drive a system into its nonlinear region of operation.

3. Where as negative feedback reduces system gain and increases bandwidth. Positive feedback increases system gain, narrows bandwidth, and becomes unstable. However, a system operating with positive feedback that hasn't gone into complete instability (oscillation), can be a very sensitive device with very high-gain amplifiers and sharp selectivity--super-regenerative radio receiver is a good example.

Answer 3

In a system with positive feedback, the system will respond to a change by extremifying the change.  In a system with negative feedback, the system will respond to the change by working to cancel it out.

Trying to balance a tennis ball on top of a basketball would be a positive feedback system.  Setting a tennis ball in a bowl would be a negative feedback system.

Answer 4

Positive feedback is telling you that you did something right, negative is when something needs improving or was an outright mistake.