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NPN common-emitter amplifier

Compare transistor bias, voltage gain, signal inversion, and clipping.

Semiconductors

Start with Bias Point, then inspect transient gain, AC gain, and clipping. Select Clipping spectrum and THD to see the output harmonics from the final four cycles. The view uses a 1 kHz fundamental, a Hann window, and five harmonics above the fundamental.

Editor showing the NPN common-emitter amplifier SPICE example as an unsaved schematic.
NPN common-emitter amplifier opens as an editable, unsaved schematic.

Open and run

  1. Open Examples from the Home ribbon.
  2. Choose NPN common-emitter amplifier.
  3. Open Simulate and choose Setup to review the analyses.
  4. Choose Run for one analysis or Run All for the complete configured set.
  5. Select a matching Scope view after the run. Use Save as sheet to keep the example or Discard to close it.
Scope showing the NPN common-emitter amplifier output spectrum and its total harmonic distortion.
Clipping adds harmonics above the 1 kHz input. The Output THD readout measures their combined level relative to the fundamental.

Sheets, analyses, and Scope

NPN common-emitter amplifier

#

Setup: Common-emitter bias, gain, and headroom

AnalysisConfiguration
1 kHz transient gainTransient
  • Step 5u
  • Stop 5m
  • Maximum step 5u
Clipping transientTransient
  • Step 5u
  • Stop 5m
  • Maximum step 5u
Small-signal voltage gainAC
  • Sweep dec
  • Points 50
  • Start 10
  • Stop 100k
Bias PointDefault settings

Scope views and expected results

Q-point voltages

Analysis: Bias Point

Bias Point
  • V(vbase)
  • V(vemitter)
  • V(vcollector)
Readouts
  • Base voltageLastV(vbase)
  • Emitter voltageLastV(vemitter)
  • Collector voltageLastV(vcollector)
Common-emitter transient response

Analysis: 1 kHz transient gain

Transient
Input and output waveforms
  • V(vin) inputV(vin)
  • V(vout) AC-coupled outputV(vout)
Readouts
  • Input swing (pk-pk)Pk-PkV(vin)
  • Linear output swing (pk-pk)Pk-PkV(vout)
Common-emitter voltage gain

Analysis: Small-signal voltage gain

AC Response
Small-signal gain
  • Vout / VinV(vout)/V(vin)
Readouts
  • Gain at 100 kHzLastV(vout)/V(vin)
Clipping / headroom

Analysis: Clipping transient

Transient
Large-signal collector
  • V(vin) 1.5 V peakV(vin)
  • V(vcollector) clippedV(vcollector)
  • V(vout)
Readouts
  • Collector maxMaxV(vcollector)
  • Collector minMinV(vcollector)
Clipping spectrum and THD

Analysis: Clipping transient

Spectrum
Output harmonics
  • V(vout)
Readouts
  • Output THDTHDV(vout)

Python scripts

No Python scripts are included with this example.

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