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

Base acceptor doping (cm^-3)

Required number in cm^-3. Acceptor doping concentration of the base. Must be a finite number greater than 0 cm^-3.

Base width (µm)

Required number in µm. Neutral base width at equilibrium. Must be a finite number greater than 0 um.

Built-in voltage (V)

Required number in V. Built-in potential of the collector-base junction. Must be a finite number greater than 0 V.

CB voltage (V)

Required number in V. Applied reverse bias on the collector-base junction. Must be a finite number at least 0 V.

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

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. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Fractional change

Returned number. Depletion widening into the base divided by the equilibrium base width (fractional change). At least 0; 0 when VCB=0.

• Material composition, geometry, process history, temperature, electric field, bias, interfaces, parasitics, and fitted parameter ranges can invalidate a compact semiconductor model.
• Base acceptor doping must be at least 5e-324.
• Base width must be at least 5e-324.
• Built-in voltage must be at least 5e-324.
• CB voltage must be at least 0.
• 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 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.

• Avalanche Breakdown Voltage Calculator

  Estimate one-sided abrupt-junction avalanche breakdown voltage from the peak critical field and depletion width: Vb ≈ Ecrit·W/2. The factor 50 converts MV/cm·µm to volts and includes the triangular-field factor of one half. The estimate neglects curvature, edge termination, and the full ionization integral.

• BJT Common-Emitter Current Gain Calculator

  Convert the common-base current gain (alpha) to the common-emitter current gain (beta) via beta=alpha/(1-alpha) with alpha in (0,1) exclusive, dimensionless. Full double precision without premature rounding; handles near-1 cancellation by checking 1-alpha finite and non-zero and beta finite, reporting numeric_overflow for extreme alpha. Ideal transistor relation neglecting recombination and series resistance; invalid for alpha<=0 or >=1.