TRANSISTOR CE AMPLIFIER
AIM: 1. To Measure the voltage gain of a CE amplifier
2. To draw the frequency response curve of the CE amplifier
Regulated power Supply (0-30V, 1A)
Resistors [33KΩ, 3.3KΩ, 330Ω, 1.5KΩ
1KΩ, 2.2KΩ, 4.7KΩ]
Capacitors- 10µF -2No
The CE amplifier provides high gain &wide frequency response. The emitter lead is common to both input & output circuits and is grounded. The emitter-base circuit is forward biased. The collector current is controlled by the base current rather than emitter current. The input signal is applied to base terminal of the transistor and amplifier output is taken across collector terminal. A very small change in base current produces a much larger change in collector current. When +VE half-cycle is fed to the input circuit, it opposes the forward bias of the circuit which causes the collector current to decrease, it decreases the voltage more –VE. Thus when input cycle varies through a -VE half-cycle, increases the forward bias of the circuit, which causes the collector current to increases thus the output signal is common emitter amplifier is in out of phase with the input signal.
1. Connect the circuit as shown in circuit diagram
2. Apply the input of 20mV peak-to-peak and 1 KHz frequency using Function Generator
3. Measure the Output Voltage Vo (p-p) for various load resistors
4. Tabulate the readings in the tabular form.
5. The voltage gain can be calculated by using the expression Av= (V0/Vi)
6. For plotting the frequency response the input voltage is kept Constant at 20mV peak-to-peak and the frequency is varied from 100Hz to 1MHz Using function generator
7. Note down the value of output voltage for each frequency.
8. All the readings are tabulated and voltage gain in dB is calculated by Using The expression Av=20 log10 (V0/Vi)
9. A graph is drawn by taking frequency on x-axis and gain in dB on y-axis
On Semi-log graph.
The band width of the amplifier is calculated from the graph
Using the expression,
Where f1 lower cut-off frequency of CE amplifier, and
Where f2 upper cut-off frequency of CE amplifier
The bandwidth product of the amplifier is calculated using the
Gain Bandwidth product=3-dBmidband gain X Bandwidth
Input voltage Vi=20mV
OUTPUT VOLTAGE (V0)
GAIN IN dB
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FREQUENCY RESPONSE: Vi=20mv
GAIN IN dB
Av=20 log10 (V0/Vi)
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INPUT WAVE FORM:
OUTPUT WAVE FORM
RESULT: The voltage gain and frequency response of the CE amplifier are obtained. Also gain bandwidth product of the amplifier is calculated.