Work out transistor gain (hfe) instantly with clear inputs, formula shown and shareable results.
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.
Current gain
hFE = Ic / Ib; Ie = Ic + Ib; alpha = Ic / Ie = hFE / (hFE + 1)
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.
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.
hFE is the DC ratio at an operating point; lower-case hfe is the small-signal AC current gain, and they differ somewhat.