22-03-2014, 10:06 AM
Common Emitter (CE) Amplifier
Aim:
To (i) calculate Gain of the amplifier (ii) find out the clipping voltages for positive and
negative polarity peaks of the output signal, (iii) study the frequency response to calculate
bandwidth for sinusoidal, square and triangular waves, (iv) compare the input and output
frequency spectrum.
Procedure:
1. Connect the input sinusoidal signal at point B as shown in Fig. 2.1 using DC blocking
capacitor. Connect load resistance at C with another DC blocking capacitor as shown in
the circuit to take output across the load.
2. Connect input and output signal to the oscilloscope. Calculate the gain of this amplifier
by taking the ratio of the output and the input amplitude. Make sure that both the input
and output sine waves are not clipped or distorted in any way. If they are reduce the
amplitude of the input sine wave until nice clean looking sine waves are present at both
input and output terminals. Also note the polarity of output sine wave relative to the
applied input signal.
3. Slowly increase the amplitude of the input sine wave until the output sinusoidal wave
begins to clip. Note the voltage at which clipping is on the positive or negative polarity
peaks.
4. Keep increasing the input voltage until the other polarity peak of the sine wave output
begins to clip and not down the voltage at which it occurs.
5. Tabulate the variation of voltage gain with frequency of the input sinusoidal, square and
triangular waves and plot frequency