Transistor Current Gain (β)
β = IC / IB
Quick answer
This calculator solves β = IC / IB for Current Gain. With Collector Current 20 mA, Base Current 50 µA, the result is 400. It solves in 3 directions, so you can enter the values you have and get the one you need.
Calculator
Formula
Description
Beta (also called hFE) is the DC current gain of a bipolar junction transistor, defined as the ratio of collector current to base current. It quantifies the transistor's amplification ability: a small base current controls a much larger collector current. Typical beta values range from 50 to 500, but beta varies significantly with collector current, temperature, and manufacturing tolerances. Good circuit design should never depend on a precise beta value; instead, use feedback or design for the minimum guaranteed beta from the datasheet.
Variables
- β — DC current gain (dimensionless)
- IC — Collector current (A)
- IB — Base current (A)
Practical Notes
Beta decreases at very low and very high collector currents. Temperature increases beta by roughly 0.5-1% per °C. For switching applications, drive enough base current to ensure saturation at minimum beta. For amplifier design, use negative feedback to make gain independent of beta. Darlington pairs multiply beta values, achieving gains of 1000-10000.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| beta | Current Gain | — | — |
| Ic | Collector Current | mA | pA, nA, µA, mA, A, kA |
| Ib | Base Current | µA | pA, nA, µA, mA, A, kA |
Step by step
- 1. What you know: Collector Current 20 mA, Base Current 50 µA
- 2. The relation: β = IC / IB
- 3. Substitute: Ic = 20 mA, Ib = 50 µA
- 4. Result: Current Gain = 400
Worked examples
Minimum range
Given: Collector Current 100 µA, Base Current 100 nA
Result: Current Gain = 1000
Low range
Given: Collector Current 1 mA, Base Current 1 µA
Result: Current Gain = 1000
Typical
Given: Collector Current 20 mA, Base Current 50 µA
Result: Current Gain = 400
High range
Given: Collector Current 0.5 A, Base Current 0.5 mA
Result: Current Gain = 1000
Maximum range
Given: Collector Current 5 A, Base Current 5 mA
Result: Current Gain = 1000
Solving for each variable
Solve for Current Gain
Collector Current 100 µA, Base Current 100 nA → 1000
Solve for Collector Current
Current Gain 0.025, Base Current 100 nA → 2.5 nA
Solve for Base Current
Current Gain 0.025, Collector Current 100 µA → 4 mA
How Current Gain changes with Collector Current
| Collector Current (input) | Current Gain (result) |
|---|---|
| 2 mA | 40 |
| 5 mA | 100 |
| 10 mA | 200 |
| 15 mA | 300 |
| 20 mA | 400 |
| 30 mA | 600 |
| 40 mA | 800 |
| 80 mA | 1600 |
| 140 mA | 2800 |
| 0.2 A | 4000 |
Embed this calculator
Paste this into any page. It keeps working when this page updates, and credits the source.
<iframe src="https://vbatpower.com/embed/transistor-beta/" width="100%" height="460" style="border:1px solid #1f2a37;border-radius:12px" loading="lazy" title="Transistor Current Gain (β)"></iframe>
<p><a href="https://vbatpower.com/formulas/transistor-beta/">Transistor Current Gain (β)</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Transistor Current Gain (β)?
Use β = IC / IB. With Collector Current 20 mA, Base Current 50 µA, Current Gain works out to 400.
What is the current gain beta of a transistor?
Rearrange for Current Gain: with Collector Current 1 mA, Base Current 1 µA, Current Gain is 1000.
How do you calculate β bipolar transistor how calculate?
Rearrange for Current Gain: with Collector Current 20 mA, Base Current 50 µA, Current Gain is 400.
What is the formula for Transistor Current Gain (β)?
The formula is β = IC / IB. Beta (also called hFE) is the DC current gain of a bipolar junction transistor, defined as the ratio of collector current to base current.
How do you find Collector Current when you know the other values?
Rearrange for Collector Current: with Current Gain 0.025, Base Current 100 nA, Collector Current is 2.5 nA.
How do you find Base Current when you know the other values?
Rearrange for Base Current: with Current Gain 0.025, Collector Current 100 µA, Base Current is 4 mA.
Related Concepts
All Semiconductors formulas →Need more features?
Save calculations, import telemetry data, simulate battery discharge, and collaborate with your team.
Try the App