BJT h-Parameters Calculator
Compute BJT small-signal hybrid parameters (hie, hfe, hre, hoe) from bias point and beta. The classic 4-terminal model used in textbook amplifier analysis.
How to Use
- Enter DC bias point: collector current Ic, beta (hfe), and Early voltage Va.
- Tool computes hie (input Z), hfe (current gain), hoe (output admittance), and hre (reverse voltage transfer — usually negligible).
Show Work
Formulas
History of h-Parameters
The hybrid (h) two-port parameter set was standardized by the IRE (now IEEE) in 1956 as the preferred small-signal characterization for BJTs. The h-parameters mix voltage and current variables (hence 'hybrid') because they match BJT behavior better than pure Z or Y parameters. By the 1990s SPICE-era design had largely shifted to the pi-model (r_pi, gm, ro), but h-parameters still appear in datasheets and textbooks as the standard characterization.
About This Calculator
Enter bias current Ic, beta (datasheet typical), Early voltage Va (typically 50-150 V for signal BJTs), and temperature. The tool computes h-parameters using Vt = kT/q (26 mV at 300 K), hie = β·Vt/Ic, hoe = Ic/Va, and equivalent pi-model gm, rπ, ro.
These are small-signal AC parameters — valid at a specific bias point. For large-signal analysis (switching, power stages), use the Ebers-Moll or Gummel-Poon SPICE model instead. Everything runs client-side.
About the BJT h-Parameters Calculator
Meet the BJT h-Parameters Calculator: a free, no-fuss tool for electronics and circuit design with nothing to install and no sign-up. Compute BJT small-signal hybrid parameters (hie, hfe, hre, hoe) from bias point and beta. The classic 4-terminal model used in textbook amplifier analysis.
How it works
Put each value in its box and read the answer as you go. Because it recalculates live, you can play with the inputs to see how each one moves the result — handy for checking your own working or planning ahead. Everything happens on your device, so it is fast and private.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
What are h-parameters?
Hybrid 2-port parameters: V_be = hie·Ib + hre·Vce; Ic = hfe·Ib + hoe·Vce. The "hybrid" means mixed V and I variables — more intuitive than pure-Z or pure-Y parameter sets for BJT characterization.
Still used?
SPICE uses pi-model (rπ, gm, ro) instead, but h-parameters are still standard in textbooks and datasheets. Converting: rπ = hie, gm = hfe/hie, ro = 1/hoe.
Temperature effects?
hie ≈ 26mV/Ib at room temp; scales inversely with Ic. hfe rises ~0.5%/°C, Va rises slightly with temperature. hre is usually < 10⁻⁴, ignorable for most designs.
How do I use the BJT h-Parameters Calculator?
Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.
Do I need to install or sign up for anything?
Not at all — it runs in the browser with nothing to install and no account. After it loads once, it even works without an internet connection.
Is my information private?
Yes. Everything happens in your browser. Nothing you type is sent to a server or saved anywhere.
Common Use Cases
CE Amp Analysis
Hand-analysis of common-emitter gain: A = -hfe·R_L/(hie + (1+hfe)·R_E).
Input/Output Z
Z_in = hie (common-emitter); Z_out ≈ 1/hoe (high impedance in CE).
Compare to pi
Verify SPICE pi-model parameters (rπ, gm, ro) against h-parameter equivalents.
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