26-09-2013, 03:25 PM
To verify the characteristics of pre emphasis and De-emphasis circuits
Pre-emphasis
The circuits are the transmitting side of the frequency modulator. It is used to increase the gain
of the higher frequency component as the input signal frequency increased, the impendence of
the
collector voltage increase. If the signal frequency is lesser then the impendence decrease which
increase the collector current and hence decrease the voltage.
TEST PROCEDURE
1. The circuit connection are made as shown in the circuit diagram for the pre-emphasis and
deemphasis
circuits
2. A power supply of 10V is given to the circuit
3. For a constant value of input voltage the values of the frequency is varied and the output is
noted on the CRO
4. A graph is plotted between gain and frequency
5. The cut frequencies are practical values of the values of cut off frequency \are found,
compared and verified.