Use this electronics calculation for a first-pass component, converter, signal, motor, or sensor estimate when the stated operating conditions and units match the device data.

Emitter voltage

Required number input.

Emitter current

Required number input.

Compute the emitter resistor value in ohms from the emitter voltage and emitter current. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Emitter resistor

The resulting emitter resistor returned as a number.

• BJT calculations using a fixed current gain or junction drop are operating-point approximations. Gain, Early effect, saturation voltage, leakage, temperature, frequency, bias network loading, and safe operating area vary by device and conditions.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check the result against the current datasheet and worst-case operating corners, then verify the circuit or measurement with simulation and bench testing where failure matters.

• Base Resistor Value

  Compute the base resistor value in ohms for a bipolar junction transistor from the control voltage, base-emitter voltage, and base current.

• Collector Resistor Value

  Compute the collector resistor value in ohms for a bipolar junction transistor from the supply voltage, saturation voltage, and collector current.

• BJT Early Voltage Effect

  Estimate collector current at a new collector-emitter voltage using the linear Early-effect model at fixed base drive.