04-01-2013, 04:37 PM
COMMON EMITTER AMPLIFIER
[attachment=46535]
THEORY:
The CE amplifier is a small signal amplifier. This small signal amplifier accepts low
voltage ac inputs and produces amplified outputs. A single stage BJT circuit may be
employed as a small signal amplifier; has two cascaded stages give much more
amplification.
Designing for a particular voltage gain requires the use of a ac negative feedback to
EC-I Lab Manual EC-261
BAPATLA ENGINEERING COLLEGE (Autonomous):: BAPATLA
stabilize the gain. For good bias stability, the emitter resistor voltage drop should be
much larger than the base -emitter voltage. And Re resistor will provide the required
negative feedback to the circuit. CE is provided to provide necessary gain to the circuit. All
bypass capacitors should be selected to have the smallest possible capacitance value, both
to minimize the physical size of the circuit for economy. The coupling capacitors should
have a negligible effect on the frequency response of the circuit.
PROCEDURE:
1. Connect the circuit as per the circuit diagram.
2. Give l00Hz signal and 20mv p-p as Vs from the signal generator
3. Observe the output on CRO and note down the output voltage.
4. Keeping input voltage constant and by varying the frequency in steps
100Hz-1MHz, note down the corresponding output
voltages.
5. Calculate gain in dB and plot the frequency response on semi log sheet
[attachment=46535]
THEORY:
The CE amplifier is a small signal amplifier. This small signal amplifier accepts low
voltage ac inputs and produces amplified outputs. A single stage BJT circuit may be
employed as a small signal amplifier; has two cascaded stages give much more
amplification.
Designing for a particular voltage gain requires the use of a ac negative feedback to
EC-I Lab Manual EC-261
BAPATLA ENGINEERING COLLEGE (Autonomous):: BAPATLA
stabilize the gain. For good bias stability, the emitter resistor voltage drop should be
much larger than the base -emitter voltage. And Re resistor will provide the required
negative feedback to the circuit. CE is provided to provide necessary gain to the circuit. All
bypass capacitors should be selected to have the smallest possible capacitance value, both
to minimize the physical size of the circuit for economy. The coupling capacitors should
have a negligible effect on the frequency response of the circuit.
PROCEDURE:
1. Connect the circuit as per the circuit diagram.
2. Give l00Hz signal and 20mv p-p as Vs from the signal generator
3. Observe the output on CRO and note down the output voltage.
4. Keeping input voltage constant and by varying the frequency in steps
100Hz-1MHz, note down the corresponding output
voltages.
5. Calculate gain in dB and plot the frequency response on semi log sheet