Use this semiconductor calculation for first-order device, material, fabrication, interconnect, packaging, or reliability estimates when every coefficient and unit convention is known.

Collector current (mA)

Required number in mA. Quiescent collector current in active mode. Must be greater than 0 mA because Early voltage is undefined at zero current.

Output conductance (S)

Required number in S. Small-signal output conductance dIC/dVCE at the Q-point. Must be greater than 0 S.

The cited overview of Bipolar junction transistor supplies background for the terminology and domain context used by this tool.^[1]

Compute the BJT Early voltage as collector current divided by small-signal output conductance, VA = IC / go. IC is quiescent collector current in mA and go is dIC/dVCE in S. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Early voltage (V)

Returned number in V. Early voltage extrapolated to zero collector current. Positive magnitude; larger VA means higher output resistance.

• Material composition, geometry, process history, temperature, electric field, bias, interfaces, parasitics, and fitted parameter ranges can invalidate a compact semiconductor model.
• Collector current must be at least 5e-324.
• Output conductance must be at least 5e-324.
• Use finite inputs in the displayed units, preserve source measurements and assumptions, and independently verify consequential decisions.

Compare the estimate with measured process data, current device documentation, and a higher-fidelity circuit, field, thermal, quantum, or TCAD model when the decision requires it.

• BJT Output Conductance Calculator

  Compute the BJT small-signal output conductance as collector current divided by Early voltage, go = IC / VA. IC is quiescent collector current in mA and VA is Early voltage in V.

• BJT Base Width Modulation Calculator

  Quantify BJT base-width modulation (Early effect) from the reverse-biased collector-base junction: fractionalChange = (sqrt(Vbi+VCB)-sqrt(Vbi))·sqrt(2·εSi/(q·NA)) / Wb, with Vbi=builtInVoltageV>0 V, VCB=collectorBaseVoltageV>=0 V, NA=acceptorDopingPerCm3>0 cm^-3, Wb=baseWidthUm>0 um, εSi=11.7·ε0 F/cm, q=1.602e-19 C. Uses stable sqrt difference; checks total voltage finiteness and depletion-factor overflow. One-sided abrupt-junction approximation neglecting emitter side and non-uniform doping; valid for NA not too low and moderate VCB; result >=0, zero when VCB=0.

• BJT Punch-Through Voltage Calculator

  Compute the total collector-base junction potential required for the depletion region to span a uniformly doped neutral base: Vtotal=q·NB·WB²/(2·εSi). This is not the externally applied reverse bias; subtract the junction built-in potential to estimate that bias.