Common-Emitter Amplifier Simulation

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Here’s the simulated result for a common-emitter stage using a 2N2222. For a standalone theoretical circuit like this, direct simulation is the right workflow .

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Results

Table

MetricValue
DC base voltage0.728 V
DC emitter voltage0.000 V
DC collector voltage0.0489 V
Collector waveform center52.5 mV
Collector swing41.6 mV to 63.4 mV
Output peak-to-peak21.79 mV
Input peak-to-peak20.00 mV
Voltage gain, transient-1.09 V/V
Voltage gain, small-signal AC at 1 kHz-0.96 V/V
Output waveform over 5 ms
A good fit to the simulated collector waveform is:
vC(t)≈52.47 mV−10.90 mVsin⁡(2π⋅1000 t)v_C(t) \approx 52.47 \text{ mV} - 10.90 \text{ mV}\sin(2\pi \cdot 1000\, t)
Reported gain
The amplifier is inverting, so the reported voltage gain is:
Av≈−1.09A_v \approx -1.09
Important observation
This bias point drives the transistor into deep saturation:
VCE≈0.0489 VV_{CE} \approx 0.0489 \text{ V}
For a BJT amplifier, (V_{CE}) should be comfortably above about 0.3 V to stay out of saturation; otherwise the stage is not operating as a proper linear common-emitter amplifier . That’s why the gain is only about -1 instead of a larger negative voltage gain.
If you want, I can next simulate a corrected bias network for the same 2N2222 so it operates in the active region and gives a more realistic common-emitter gain.
Fix the bias
Add emitter resistor
Run frequency sweep
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