FEEDBACK AMPLIFIERS
FEEDBACK AMPLIFIERSWhat is feedback amplifier?If an amplifier
has feedback path exists from output to input then that amplifier
is termed as Feedback amplifier.
Feed back is the parameter which quantifies the amount of
feedback given in a feedback amplifier.Feedback factor = Feedback
signal/input signal.What is negative and positive feedback?If
feedback from output to input is given in such in a way that the
introduction of feedback in the amplifier decreases the overall
gain, then the feedback is termed asnegative feedback.If feedback
from output to input is given in such in a way that the
introduction of feedback in the amplifier increases the overall
gain, then the feedback is termed aspositive feedback.
What are Advantages and disadvantages of Negative feedback?
Some of the Advantages of negative feedback:a) Input resistance
increasesb) Output resistance decreasesc) Bandwidth increasesd) Non
linear distortion decreasese) Frequency distortion decreasesf)
Sensitivity will be decreasedg) Gain stability
The main disadvantage of negative feedback is decrease inoverall
gain. The gain and feedback factor in an amplifier areoften
functions of frequency, so the feedback may lead topositive
feedback.
What is de-sensitivity factor?
De sensitivity factor is defined as the factor with which the
feedbackdesensitizes the gain. It is also called as return
difference.
De sensitivity factor = (dAfb/Afb)/(dA/A) = 1/(1+A*) Where Afb
is gain with feedback A is gain without feedback is feedback
factor.What is a loop gain in amplifier?
Loop gain in amplifier is defined as the gain of feedback path
from output to input. It is the product of loop gain and feedback
factor in positive feedback amplifiers. In negative feedback
amplifiers it is the negative product of loop gain and feedback
factor.What is the effect of negative feedback on voltage gain, BW,
Noise, nonlinear distortion, Ri, Ro of a voltage amplifier?
The voltage gain, bandwidth, noise, nonlinear distortion,
inputresistance, output resistance are
Voltage gain with feedback = Voltage gain without feedback* de
sensitivity factor (since de sensitivity factor
