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.

Control voltage

Required number input.

Base-emitter voltage

Optional number input.

Base current

Required number input.

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

Base resistor

The resulting base resistor returned as a number.

• Compact electronics formulas omit some combination of tolerances, temperature drift, bandwidth, loading, parasitics, noise spectrum, nonlinearity, clipping, calibration, layout, and device-specific limits. Typical datasheet values are not guaranteed limits.
• 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.

• Collector Resistor Value

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

• Emitter Resistor Value

  Compute the emitter resistor value in ohms from the emitter voltage and emitter current.

• BJT Early Voltage Effect

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