13-09-2013, 02:31 PM
CURRENT-SERIES FEEDBACK AMPLIFIER
Aim:
To design and test the current-series feedback amplifier and to calculate the
following parameters with and without feedback.
1. Mid band gain.
2. Bandwidth and cut-off frequencies.
3. Input and output impedance.
Theory:
The current series feedback amplifier is characterized by having shunt sampling
and series mixing. In amplifiers, there is a sampling network, which samples the output
and gives to the feedback network. The feedback signal is mixed with input signal by
either shunt or series mixing technique. Due to shunt sampling the output resistance
increases by a factor of ‘D’ and the input resistance is also increased by the same factor
due to series mixing. This is basically transconductance amplifier. Its input is voltage
which is amplified as current.
Procedure:
1. Connect the circuit as per the circuit diagram.
2. Keeping the input voltage constant, vary the frequency from 50Hz to 3MHz in
regular steps and note down the corresponding output voltage.
3. Plot the graph: Gain (dB) Vs Frequency
4. Calculate the bandwidth from the graph.
5. Calculate the input and output impedance.
6. Remove Emitter Capacitance, and follow the same procedures (1 to 5).
Result:
Thus the current series feedback amplifier is designed and constructed and the
following parameters are calculated.