+ve & -ve feedback in opamps

Thread Starter

aamirali

Joined Feb 2, 2012
415
1. How to solve for circuits having both +ve & -ve feedback at same time.

2. -ve feedback will tend to make v1=v2., while +ve feedback will take voltage at one pin greater than other so that it get saturated.

How does equilibrium establish between two opposite work forces.
 

Audioguru

Joined Dec 20, 2007
11,251
Positive feedback is used in oscillators and latches. Negative feedback is used in amplifiers.
 

cabraham

Joined Oct 29, 2011
82
Positive feedback is used in oscillators and latches. Negative feedback is used in amplifiers.
Usually that's the case, but there are exceptions. I have a patent on a logarithmic photodiode amp, U.S. no. 5,670,775. It uses both positive as well as negative feedback to perform amplification. As long as the net feedback remains negative, the system is stable.

Care must be exercised when using positive feedback in amp systems. Stability must be carefully examined, but it can be done. I've had success with mixed feedback amps, albeit I use them rarely.

Claude
 

Thread Starter

aamirali

Joined Feb 2, 2012
415
I was talking abt ckt having both +ve & -ve feedback at same time. How to analyse them.
 

cabraham

Joined Oct 29, 2011
82
Read any of the books by Jerald Graeme, formerly with Burr-Brown, Jerald addresses the mixed feedback behavior, & how to stabilize.
 
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