๐ŸŽ›๏ธ Electronics Design Tool

Voltage Divider &
Regulator

Design voltage divider networks and LM78xx / LM317 regulator circuits. Compute resistor values, power dissipation and efficiency.

Voltage Div.LM317RegulatorPower Calc
๐Ÿ”€ Voltage Divider Calculator

A resistive voltage divider produces a fraction of the input voltage across R2. Enter any 3 values to compute the 4th.

Input Parameters
Load (Optional)
Results
โ€”
Vout
Volts
โ€”
Voltage Ratio
Vout/Vin
โ€”
Current
mA
โ€”
Power Dissipated
mW
Circuit Diagram
Vin
Input
R1
โ€”
Vout
Output
R2
โ€”
GND
Ground

Formula: Vout = Vin ร— R2 / (R1 + R2)

With Load: R2_eff = R2 โˆฅ RL = (R2 ร— RL) / (R2 + RL)

โšก LM317 Adjustable Regulator

The LM317 output voltage is set by R1 and R2. Vout = 1.25 ร— (1 + R2/R1). Typically R1 = 240ฮฉ.

Input Parameters
Results
โ€”
R2 Required
ฮฉ
โ€”
Actual Vout
V
โ€”
Voltage Drop
V
โ€”
Power Dissipated
W
โ€”
Efficiency
%
โ€”
Output Power
W
โš ๏ธ High power dissipation โ€” heatsink recommended!

Formula: Vout = 1.25 ร— (1 + R2/R1) + Iadj ร— R2

R2 = R1 ร— (Vout/1.25 โˆ’ 1)

Pdiss = (Vin โˆ’ Vout) ร— Iload

๐Ÿ”ง LM78xx Fixed Regulator

LM78xx series provides fixed output voltages. Select the IC and enter input voltage to get dissipation analysis.

Input Parameters
Results
โ€”
Output Voltage
V
โ€”
Voltage Drop
V
โ€”
Power Dissipated
W
โ€”
Efficiency
%
โ€”
Junction Temp
ยฐC
โ€”
Status

Min Vin: Vout + 2V (dropout voltage)

Max Vin: 35V (LM78xx series limit)

Pdiss = (Vin โˆ’ Vout) ร— Iload  |  Tjunc = Tamb + Pdiss ร— ฮธJA