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.

Supply voltage

Required number input.

Saturation voltage

Optional number input.

Collector current

Required number input.

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

Collector resistor

The resulting collector 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.

• 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.

• Emitter Resistor Value

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

• Decoupling Cap Value

  Compute the decoupling capacitance C = I x dt / dV needed to supply a transient current for a droop time within an allowed droop voltage.