Transistor Bias Calculator
Calculate the base resistor for a BJT in common-emitter configuration to set a target collector current.
V
V
mA
Base Resistor
113,000 Ω
Base Current100.0 µA
Transistor Power120.0 mW
Base Resistor vs Supply Voltage (Vcc)
BJT Transistor Biasing
In common-emitter configuration a base resistor sets the operating point.
Formula
I_B = I_C / hFE
R_B = (Vcc - V_BE) / I_B
Where hFE is DC current gain and V_BE is typically 0.7 V for silicon. This simple bias is beta-dependent; voltage divider bias provides better stability.
Example Calculation
Bias a transistor with hFE=100 for 10 mA collector current from 12 V.
- 01I_B = 10 mA / 100 = 0.1 mA = 100 uA
- 02R_B = (12 - 0.7) / 0.0001 = 113,000 ohms (113k)
- 03Power = 12 x 10 = 120 mW
Frequently Asked Questions
Learn More
Ohm's Law Guide
A complete guide to Ohm's Law. Learn the relationship between voltage, current, and resistance, with practical examples, the power triangle, and circuit analysis tips.