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.
Description
Calculate the total depletion-supporting potential needed for a BJT collector depletion region to span the neutral base.
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.
When to use BJT Punch-Through Voltage Calculator
- Calculate the total depletion-supporting potential needed for a BJT collector depletion region to span the neutral base.
- Compare fabrication or device scenarios while holding coefficients and unit conventions constant.
- Check a hand calculation before moving to a higher-fidelity process, circuit, or TCAD model.
How the calculation works
The result includes junction built-in potential; subtract Vbi to estimate the externally applied collector-base reverse bias.
Vtotal = q·NB·WB²/(2εSi) Interpreting the result
The result includes junction built-in potential; subtract Vbi to estimate the externally applied collector-base reverse bias.
Assumptions and limitations
- Uniform base doping, a one-sided abrupt junction, planar geometry, and complete depletion at punch-through are assumed.
- Use parameters measured for the same material, geometry, temperature, and operating regime whenever the result informs engineering work.