What is meant by feedback in amplifiers?what is the difference between negative and positive fedback

Question

What is meant by feedback in amplifiers?what is the difference between negative and positive fedback

Answer 1

The words are actually self-explanatory.....

An amplifier amplifies an alectric signal.

Now you can take that amplified signal from the output, and bring (some of it) back to the input again, to amplify it even more -- you have a positive feedback. That can get "out of hands" and the amplifier starts to oscillate. You control the frequency that gets fed-back (with a R/C or L/C circuit), and you have an oscillator.

While for above, the phase of the signal at the input and output must be the same, you can also take the output signal, inverse its phase, and feed it back to the input -- you have a negative feedback. Again, you control the frequency that gets fed-back (with a R/C or L/C circuit), and you have a filter which supresses certain frequencies.

Op-Amp ICs have conveniently 2 inputs, one "+" for positive feedback, and "-" for negative feedback.

Answer 2

Feedback: obtain some signal from output stage,then injects it to the input stage.

Negative feedback: very common use in sound amplifier to improve the frequency response,reducing sound distortion. Feedback signal is 180 degree out of phase compare to the input.

Positive feedback: very common use in oscillator circuit. Feedback signal is 0 degree in phase compare to the input.

Answer 3

Amplifier is an equipment that amplify signals such as speech signal or video signal. Depending on the amplifier type and circuit components, the amplifier has a certain  values for the Gain and Bandwidth so that the Gain Bandwidth product is constant. If we require to broaden the bandwidth, the gain must be reduced. This can be performed using Feedback. That is feeding back a part from the amplifier output to the amplifier input after making a 180 degree phase shift between output and input. This is called negative feedback. Therefore, negative feedback is used to broaden the bandwidth and lower the Gain. On the other hand, if the input and the feeded back signal are in-phase, this will accomplish positive feedback. Positive feedback is usually used in Oscillators design. This is due to the fact that oscillator has no input signal and provides an output signal with single frequency. That is a very sharp bandwidth(single frequency) and

very high (almost infinite) gain.  

Answer 4

Feedback !!! its a concept used in amplifiers

in simple terms.. feedback means..mixing the output signal of an amplifier with the input. here the signal may imply voltage or current.

positive feedback : If the phase difference between output and the input signals is 0 degrees or 360 degrees, then the  output signal overlaps with the input signal ina constructive way !! ansd hence the resultant signal increases..

negative feedback: If the phase difference between output and the input signals is 180 degrees..  then the  output signal overlaps with the input signal in a destructive way !! and hence the resultant signal decreases.. this concept is called as negative feed back

this is a simple explaination for detailed explaination refer...

Answer 5

feedback amplifires gives maximum band width,it process is very easily

there is two type feed back positive & negative feed back.but negative feedback is more useful then positive feed back.