Single transistor amplifier

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The schematic is wired as shown in the diagram below. It is very similar to the schematic used for the output characteristics. The AC signal is connected to the base, through a capacitor so that the biasing is not affected. Since the gain is high, we need a small input signal, smaller than the 80 mV available from WG. A divider network using 1k and 2.2k gives around 20 mV output and that is fed to the base. This input signal is monitored on A2. The DC operating point is decided by the voltage applied to the base through the 100k resistor. By adjusting PV2, we can take the transistor between cut-off and saturation conditions. The value of PV2 is adjusted to get an output with minimum distortion. To improve it further, one can reduce the input signal, use a higher collector supply voltage instead of PV1, or use a transistor with a lower gain value.

The result shown is using 2N2222 NPN transistor.


using SEELab3

SEELab3 has the option of reducing the amplitude of WGbar by connecting a gain resistor. A 100 Ohm may be used to reduce the 3 volts to around 30 mV.