Zener Regulator Calculator
Design a simple zener diode voltage regulator. Calculate the series resistor value and power ratings.
V
V
mA
mA
Series Resistor
276.0 Ω
Resistor Power172.5 mW
Zener Power127.5 mW
Series Resistor vs Input Voltage
Zener Diode Voltage Regulator
A zener diode in reverse breakdown maintains a nearly constant voltage.
Formula
R_series = (V_in - V_zener) / (I_load + I_zener_min)
The resistor drops excess voltage. The zener must carry at least its minimum current for proper regulation even at full load.
Example Calculation
Regulate 12 V down to 5.1 V for a 20 mA load. Zener needs 5 mA minimum.
- 01Total current = (20 + 5) / 1000 = 0.025 A
- 02R = (12 - 5.1) / 0.025 = 276 ohms
- 03Resistor power = 6.9 x 0.025 x 1000 = 172.5 mW
- 04Zener power = 5.1 x 0.025 x 1000 = 127.5 mW
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