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Transistor Gain (hFE) Calculator

Work out transistor gain (hfe) instantly with clear inputs, formula shown and shareable results.

About Transistor Gain (hFE) Calculator

Current gain hFE is collector current divided by base current. Emitter current is the sum of the two, and alpha (hFE/(hFE+1)) is the common-base gain, always just under unity. hFE varies widely between samples and with current, which is why designs must not depend on its exact value.

Formula

Current gain

hFE = Ic / Ib; Ie = Ic + Ib; alpha = Ic / Ie = hFE / (hFE + 1)

Worked example

With the default values below, Transistor Gain (hFE) Calculator returns Current gain hFE of 125.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Collector current
50 mA
Base current
0.4 mA
Collector-emitter voltage
5 V

Results

Current gain hFE
125.00 x
Emitter current
50.40 mA
Common-base gain alpha
0.99206
Collector dissipation
250.00 mW

Step by step

  1. 1Values used
  2. 2Current gain
  3. 3Current gain hFE= 125.00 x
  4. 4Emitter current= 50.40 mA
  5. 5Common-base gain alpha= 0.99206
  6. 6Collector dissipation= 250.00 mW

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

Frequently Asked Questions

Why can I not rely on hFE?

It typically spans 3:1 or more within one part number and changes with collector current and temperature. Good designs use feedback so gain does not depend on it.

What is the difference between hFE and hfe?

hFE is the DC ratio at an operating point; lower-case hfe is the small-signal AC current gain, and they differ somewhat.

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Transistor Gain (hFE) Calculator | Calcrivo