Hi all - I wonder if any of you guys can settle an argument.
I say that in a simple class A BJT amp, only NEGATIVE feedback is used, but a friend reckons both negative AND positive feedback are used. I always thought positive feedback would reduce the stability of the output and was undesirable in an amplifier, unless it was being used as an oscillator.
Can anyone help?
Thanks in advance - Den.
in article cajnhm$14r$ snipped-for-privacy@newsg4.svr.pol.co.uk, Den at snipped-for-privacy@spamfree.freeserve.co.uk wrote on 6/14/04 1:25 AM:
Although not used much now, regenerative detectors were often used to provide sensitive and narrow band detectors. It was amazing how a one-tube, now it would be a one transistor, receiver could pull in signals. They were used just below the oscillation gain for AM signals and barely oscillating to detect CW (A1) signals.
Bill
Basically there is no such thing as positive or negitive feedback. There is only feedback. The phase angle of the feedback determines whether it acts as positive or negitive feedback. Positive phase feedback is generally used as a load correction in a power supply.
I prefer what is called, Feed forward, to feedback
Feed forward does not effect the stability of an amplifier and corrects for line variations.
feed forward takes a voltage dependent on the input voltage to correct output variations to line fluctuations. See Google for some of my papers on this subject.
Have something to add? Share your thoughts — no account required.
Ask the community — no account required