Transistor Biasing Calculator

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Voltage divider is the most stable and widely used; fixed bias is the simplest but sensitive to beta variations.
DC power supply voltage connected to the collector side.
V
DC current gain hFE of the transistor. Check the datasheet; typical silicon BJTs: 50-300.
Junction forward voltage. 0.7 V for silicon (default); 0.3 V for germanium.
V
Top resistor of the voltage-divider network that sets base voltage.
kΩ
Bottom resistor of the voltage-divider network, connected to ground.
kΩ
Load resistor at the collector terminal.
kΩ
Emitter degeneration resistor. Set to 0 for no emitter resistor (fixed/CFB topologies often omit it).
kΩ
External AC load resistor. Used to compute effective AC collector resistance Rc'||RL for voltage gain.
kΩ
Collector current (Ic)Active region
2.971mA

DC quiescent collector current - the main Q-point current

Base voltage (Vb)2.11V
Emitter voltage (Ve)1.41V
Collector voltage (Vc)5.464V
Base current (Ib)29.71μA
Emitter current (Ie)3.001mA
Collector-emitter voltage (Vce)4.053V
Operating regionActive (linear region)
Voltage gain (Av)3.77
Input impedance (Zin)1.74kΩ
Output impedance (Zout)2.2kΩ
Stability factor (S)4.66
4.053 V
Saturation<0.2Active region0.2-12.5Near cutoff12.5+

Voltage divider bias: Ic = 2.97 mA, Vce = 4.05 V (Active)

  • Voltage gain is 3.8x. Adding a bypass capacitor across Re will increase gain toward Rc / re.
  • Stability factor S = 4.7: excellent thermal stability.

Next stepTo set the Q-point for maximum swing, aim for Vce near Vcc/2 and Ic in the linear region. Use a bypass capacitor across Re to maximize AC gain without sacrificing DC stability.

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