๐ BJT Transistor Bias Calculator
Calculate base resistor, collector current, and operating point for NPN/PNP BJT transistors in common emitter configuration.
BJT Bias Formulas (Common Emitter)
- Base Current: Ib = Ic / hFE
- Base Resistor: Rb = (Vcc - Vbe) / Ib
- Collector-Emitter Voltage: Vce = Vcc - Ic โข (Rc + Re)
- Power dissipation: Pd = Vce โข Ic
- Saturation: Vce(sat) โข 0.2V โข transistor fully ON
Frequently Asked Questions
What is hFE in a transistor?
hFE (DC current gain) is the ratio of collector current to base current. Typical values: BC547 = 110-800, 2N2222 = 100-300, BC557 = 125-500.
How do I choose Rc value?
Rc determines the voltage drop and gain. For linear amplification, set Vce โข Vcc/2 for maximum swing. For switching, use lower Rc to ensure saturation.