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.

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

Compute the BJT emitter injection efficiency assuming equal diffusion coefficients on both sides. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Gamma

Returned number. Fraction of emitter current carried by carriers injected into the base.

• 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-Base Current Gain Calculator

  Compute the BJT common-base current gain alpha as the product of emitter efficiency and base transport factor.

• BJT Base Transport Factor Calculator

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

• Diffusion Capacitance Calculator

  Compute the diffusion capacitance of a forward-biased diode from stored-charge lifetime and current. Formula: Cdiff [nF] = 1e9 · (τ [ns]·1e-9 · I [mA]·1e-3) / (n · Vt [V]), where Vt = k·T/q (k=1.380649e-23 J/K, q=1.602176634e-19 C). Equivalent: Cdiff [F] = τ·I/(n·Vt). Inputs: I ≥ 0 mA, τ > 0 ns, n ≥ 1 (default 1), T > 0 K (default 300 K). Output: Cdiff ≥ 0 nF. Assumes low-level injection, negligible depletion capacitance, and quasi-neutral stored charge τ·I.