AIM: 1. ToMeasure the voltage gain of a CE amplifier
2. To draw the frequency responsecurve of the CE amplifier
APPARATUS:
TransistorBC-107
Regulated power Supply(0-30V, 1A)
FunctionGenerator
CRO
Resistors [33KΩ, 3.3KΩ, 330Ω, 1.5KΩ
1KΩ, 2.2KΩ, 4.7KΩ]
Capacitors- 10µF -2No
100µF
Bread Board
Connecting Wires
THEORY:
The CE amplifier provides highgain &wide frequency response. The emitter lead is common to both input& output circuits and is grounded. The emitter-base circuit is forwardbiased. The collector current is controlled by the base current rather thanemitter current. The input signal is applied to base terminal of the transistorand amplifier output is taken across collector terminal. A very small change inbase current produces a much larger change in collector current. When +VEhalf-cycle is fed to the input circuit, it opposes the forward bias of thecircuit which causes the collector current to decrease, it decreases thevoltage more –VE. Thus when input cycle varies through a -VE half-cycle,increases the forward bias of the circuit, which causes the collectorcurrent to increases thus the outputsignal is common emitter amplifier is in out of phase with the input signal.
CIRCUIT DIAGRAM:
PROCEDURE:
1. Connectthe circuit as shown in circuit diagram
2. Applythe input of 20mV peak-to-peak and 1 KHz frequency using Function Generator
3. Measurethe Output Voltage Vo (p-p) for various load resistors
4. Tabulatethe readings in the tabular form.
5. Thevoltage gain can be calculated by using the expression Av=(V0/Vi)
6. Forplotting the frequency response the input voltage is kept Constant at 20mV peak-to-peak and the frequency is variedfrom 100Hz to 1MHz Using function generator
7. Notedown the value of output voltage for each frequency.
8. Allthe readings are tabulated and voltage gain in dB is calculated by Using The expression Av=20 log10(V0/Vi)
9. Agraph is drawn by taking frequency on x-axis and gain in dB on y-axis
On Semi-log graph.
The band widthof the amplifier is calculated from the graph
Using the expression,
Bandwidth, BW=f2-f1
Where f1 lowercut-off frequency of CE amplifier, and
Where f2 upper cut-offfrequency of CE amplifier
The bandwidthproduct of the amplifier is calculated using the
Expression
Gain Bandwidth product=3-dBmidbandgain X Bandwidth
OBSERVATIONS:
Input voltageVi=20mV
LOAD RESISTANCE(KΩ) | OUTPUT VOLTAGE (V0) | GAIN AV=(V0/Vi) | GAIN IN dB Av=20log10 (V0/Vi) |
FREQUENCY RESPONSE: Vi=20mv
FREQUENCY(Hz) | OUTPUT VOLTAGE (V0) | GAIN IN dB Av=20 log10 (V0/Vi) |
MODELWAVE FORMS:
INPUT WAVE FORM:
OUTPUTWAVE FORM
FREQUENCY RESPONSE
RESULT: The voltage gain andfrequency response of the CE amplifierare obtained. Also gain bandwidth product of the amplifier is calculated.
VIVA QUESTIONS:
1. Whatis phase difference between input and output waveforms of CE amplifier?
2. Whattype of biasing is used in the given circuit?
3. Ifthe given transistor is replaced by a p-n-p, can we get output or not?
4. Whatis effect of emitter-bypass capacitor on frequency response?
5. Whatis the effect of coupling capacitor?
6. Whatis region of the transistor so that it is operated as an amplifier?
7. Howdoes transistor acts as an amplifier?
8. Drawthe h-parameter model of CE amplifier?
9. Whattype of transistor configuration is used in intermediate stages of a multistageamplifier?
10.Whatis Early effect?
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