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

Base doping (cm^-3)

Required number in cm^-3. Base doping concentration.

Base width (µm)

Required number in µm. Neutral base width.

Emitter doping (cm^-3)

Required number in cm^-3. Emitter doping concentration.

Emitter length (µm)

Required number in µm. Minority-carrier diffusion length in the emitter.

Base diffusion length (µm)

Required number in µm. Minority-carrier diffusion length in the base; must exceed the width.

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

Compute the BJT common-base current gain alpha as the product of emitter efficiency and base transport factor. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Alpha

Returned number. Common-base current gain, just below one.

• Material composition, geometry, process history, temperature, electric field, bias, interfaces, parasitics, and fitted parameter ranges can invalidate a compact semiconductor model.
• 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 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.

• BJT Base Transport Factor Calculator

  Compute the BJT base transport factor from base width and minority-carrier diffusion length.

• APD Multiplication Factor Calculator

  Compute the avalanche photodiode multiplication factor from the Miller model M=1/[1-(V/Vb)^N]. Inputs are magnitudes: reverse-bias magnitude V≥0 V must remain below breakdown magnitude Vb>0 V (numerator V, denominator Vb; V=0 gives M=1, V→Vb- diverges). Exponent N in [1, 6] (default 2) captures the ionization coefficients. Signed voltages are not supported (use magnitudes). Result M≥1 is a dimensionless factor (per-carrier gain, not total current).