BJT small-signal amplifier
Hybrid-pi estimates for common-emitter, emitter follower and common-base stages.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
Transconductance: gm = IC / VT; VT = kT/q; rπ = β/gm
Assumptions
- Midband hybrid-pi model; Early effect, device capacitances and high-frequency rolloff are omitted.
- Common-base source drives the emitter with an AC-grounded base. Gain is collector/emitter voltage ratio.
- Swing is a first-order cutoff/saturation estimate; verify actual collector/emitter supply headroom.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Stage
- ce
- Quiescent collector current
- 0.001 A
- Beta
- 100
- Device temperature
- 25 °C
- Collector resistor
- 4700 Ω
- Total emitter resistor
- 1000 Ω
- Unbypassed emitter resistance
- 100 Ω
- AC load
- 10000 Ω
- Source resistance
- 600 Ω
- Bias network resistance
- 100000 Ω
- Input coupling capacitance
- 0.000001 F
- Output coupling capacitance
- 0.000001 F
- Emitter bypass capacitance
- 0.0001 F
- Quiescent VCE
- 6 V
Results
- Gain including source divider
- -23.9581
- Thermal voltage
- 0.0256926 V
- Transconductance
- 0.0389217 S
- Base-emitter small-signal resistance
- 2569.26 Ω
- Loaded stage voltage gain
- -25.2365
- Input resistance
- 11244.6 Ω
- Output resistance
- 4700 Ω
- Input coupling pole
- 13.4369 Hz