CLAMPERS BY SRAVANI ANNAPURNA A(221710303057)

CLAMPERS: 
A clamper is an electronic circuit that fixes entire the positive or the negative peak excursions of a siganl  to a defined value by shifting its DC value.The clamper does not restrict the peak-to-peak excursion of the signal,it move sthe whole signal up or down so as to place the peak at the reference level.A diode clamp consists of a diode,which conducts electric current in only one direction and prevents the signal exceeding the reference value;and a capicitor which provides a DC offset from the stored charge.The capicitor forms a time constant with the resistor load which determines the range of frequencies over which the clamper will be effective.
Clamper circuits are categorised by their operations like negative or positive and biased or un-biased.

 POSITIVE UN-BIASED :In the negative cycle of the input AC signal,the diode is forward biased and conducts,charging the capacitor to the peak negative value of Vin.During the positive cycle, the diode is reverse biased and thus does not conduct.The output voltage is therefore equal to the voltage stored in the capacitor plus the input voltage,so Vout=Vin+Vin-peak...
This is also called a villard circuit..

 NEGATIVE UN-BIASED :A negative unbiased circuit is the opposite of the equivalen positive clamp.In the positive cycle of the input AC signal,the diode is forward biased and conducts,charging the of the peak positive value of Vin.During the negative cycle,the diode is reverse biased and thus does not conduct.The output voltage is therefore equal to the voltage stored in the capacitor plus the 

input voltage again,so Vout=Vin-Vin-peak..                                                                                             

 POSITIVE BIASED : A positive biased voltage clamp is identical to an equivalent unbiased clamp but with the output voltage offsets by the bias amount Vbias.Thus,Vout=Vin+(Vin-peak+Vbias).

  NEGATIVE BIASED :A negative biased voltage clamper is likewise identical to an equivalent un-biased calmp but with the output voltage offset in the negative direction by the bias amount Vbias.
Thus,Vout=Vin-(Vin-peak+Vbias).

OP-AMP CIRCUIT:The figure shows an op-amp clamp circuit with a non-zero referenc clamping voltage.The advantage here is that the clamping level is at precisely the reference voltage.There is no need to take into acccount the forward volt drop of the diode.The effect of the diode volt drop on the circuit output will be divided down by the gain of the amplifier,resulting in an insignificant error.the   circuit also has a great improvement in linearity at smal input signals in comparision to the simple      diode circuit.