Lab 2: Common Emitter Amplifiers
Lab 2 was designed to familiarize us with the operation and circuit of the common emitter amplifier. It begins with biasing the transistor and then proceeds to amplifying a signal.
Section 2.4.1 - In the first section, the DC components of the CE amplifier are constructed and measured with a multimeter. This indicates the DC operating point of the amplifier. An image of the amplifier in this state is shown below. The following measurements were taken:
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Vb = 1.85V
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Vc = 5.57V
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Ve = 1.126V
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Vbe = 0.723V
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Vce = 4.44V
Section 2.4.2 - The second section added the AC components of the amplifier. The completed amplifier is shown below. This was fed a 1kHz sine wave with an amplitude of 10mV, the input and output can be seen in the oscilloscope capture below.
Section 2.4.3 - The voltage gain of this amplifier is (1.78V / 36.8mV) = 48.370. These measurements are not consistent with the capture above because after saving the capture I increased the timescale which yielded a more accurate voltage measurement.
Section 2.4.4 - This section involved plotting the gain of the amplifier with various load resistances. The data table and graph is shown below. The graph would indicate that the CE amplifier would not perform well driving an 8 ohm speaker.
Section 2.4.5 - This section involved measuring the gain of the amplifier at various input frequencies to create a Bode plot. The Bode plot shows that the 3dB bandwidth is 198kHz, from 2kHz to 200kHz.
