\[R_s=\frac{V_{in}-V_Z}{I_Z+I_L}\]
Variables
Rsseries resistor (Ω)
Vininput voltage (V)
Vzzener voltage (V)
Izzener current (A)
Ilload current (A)
Description
What is this formula?
The Zener Regulator Series Resistor formula calculates the resistor required in a Zener diode voltage regulator circuit. The resistor limits current and ensures proper Zener diode operation.
When to use it
Use this formula when designing simple voltage regulators using Zener diodes for low-power electronic circuits.
Example
A 12 V supply is used with a 5.1 V Zener diode. The load current is 15 mA and the desired Zener current is 5 mA.
Given:
Vin = 12 V
Vz = 5.1 V
Il = 0.015 A
Iz = 0.005 A
Formula:
Rs = (Vin - Vz) / (Iz + Il)
Substitution:
Rs = (12 - 5.1) / (0.005 + 0.015)
Result:
Rs = 345 Ω
A resistor of approximately 345 Ω is required.
Applications
Voltage regulation, power supply circuits, reference voltage circuits, embedded electronics, analog electronics, and protection circuits.