Electricity calculator group

Electronic Components Calculators

Calculate capacitor, inductor, LED, transistor, diode, relay, and snubber values.

Use operating values, not markings alone

Component behavior changes with voltage, current, frequency, tolerance, bias, and temperature. Use data-sheet values for the intended operating point whenever possible.

The pages here cover first-order capacitor, inductor, LED, transistor, diode, relay, and snubber relationships. Parasitics and thermal limits usually require additional checks.

Electronic Components calculators by result

Capacitor ChargingCalculate capacitor voltage during RC charging.Capacitor DischargingCalculate capacitor voltage during RC discharge.Zener ResistorCalculate series resistor from supply minus Zener voltage and zener branch current.Series CapacitorCalculate equivalent capacitance from capacitor C1 and capacitor C2.Parallel CapacitorCalculate equivalent capacitance from capacitor C1 and capacitor C2.Capacitor EnergyCalculate stored energy from capacitance and voltage.Series InductorCalculate equivalent inductance from inductor L1 and inductor L2.Parallel InductorCalculate equivalent inductance from inductor L1 and inductor L2.Inductor EnergyCalculate stored magnetic energy from inductance and current.RL Time ConstantCalculate RL time constant from inductance and resistance.LED ResistorCalculate series resistance from supply minus LED voltage and LED current.LED Series StringFind the maximum whole LED count supported by the available voltage.Transistor Base ResistorCalculate base resistor from drive voltage above VBE and required base current.BJT BiasCalculate base current from collector current and DC current gain.MOSFET Conduction LossCalculate conduction loss from drain current and on resistance.MOSFET Switching LossCalculate switching loss from energy per switching cycle and switching frequency.Diode Power DissipationCalculate diode loss from forward voltage and average current.RC Time ConstantCalculate RC time constant from resistance and capacitance.Relay Coil CurrentCalculate coil current from coil voltage and coil resistance.RC SnubberCalculate snubber time constant from resistance and capacitance.

Reactive components and time response

Series and parallel capacitor or inductor equations assume ideal uncoupled parts. Energy and time-constant pages add voltage, current, resistance, or elapsed time as needed.

Charging and discharging now calculate the exponential response directly from resistance, capacitance, and time rather than asking for a precomputed fraction.

LEDs and semiconductor losses

LED string count is rounded down so the forward-voltage sum does not exceed the available voltage. Reserve headroom for current regulation and worst-case forward voltage.

MOSFET, diode, BJT, and Zener calculations should use worst-case data-sheet values at temperature. Switching energy, conduction loss, bias gain, and pulse ratings are different constraints.

Layout and thermal reality

High-speed switching introduces loop inductance, capacitance, ringing, and EMI that ideal component equations cannot predict. Snubber values often require measurement and iteration.

Convert calculated dissipation into junction temperature using package, board, heat-sink, and airflow data before accepting a part.

Tolerance corners and combined stress

Test combinations of tolerance, supply variation, temperature, and load rather than changing each value in isolation only. The limiting component condition may occur when several ordinary deviations act in the same direction.

Check simultaneous voltage, current, pulse, and thermal stress against data-sheet curves; separate maximum ratings are not automatically valid at the same time.