+ve & -ve feedback in opamps

Discussion in 'General Electronics Chat' started by aamirali, Apr 16, 2012.

  1. aamirali

    Thread Starter Member

    Feb 2, 2012
    415
    1
    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.
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Positive feedback is used in oscillators and latches. Negative feedback is used in amplifiers.
     
  3. cabraham

    Member

    Oct 29, 2011
    82
    30
    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
     
  4. aamirali

    Thread Starter Member

    Feb 2, 2012
    415
    1
    I was talking abt ckt having both +ve & -ve feedback at same time. How to analyse them.
     
  5. cabraham

    Member

    Oct 29, 2011
    82
    30
    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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