Voltage Regulator Calculator Form
This page keeps a single-column content flow while the calculator fields expand to three columns on large screens, two on medium, and one on mobile.
Example Data Table
| Scenario | Type | Key Inputs | Main Observation |
|---|---|---|---|
| 5 V logic rail | Fixed linear | 12 V input, 5 V output, 1.0 A load, 2 V dropout | Good headroom, but dissipation becomes significant at higher current. |
| Adjustable bench rail | Adjustable linear | 15 V input, 9 V target, 240 Ω R1, 50 µA adjust current | Feedback resistor sizing determines the actual setpoint accurately. |
| Reference clamp | Zener shunt | 12 V source, 5.1 V zener, 150 Ω resistor, 20 mA load | Regulation depends on keeping enough branch current in the zener. |
Formula Used
1) Fixed Linear Regulator
Minimum input voltage: VIN,min,req = VOUT + VDROP
Input current: IIN = ILOAD + IQ
Output power: POUT = VOUT × ILOAD
Input power: PIN = VIN × IIN
Efficiency: η = (POUT / PIN) × 100
Dissipation: PD = (VIN − VOUT) × ILOAD + VIN × IQ
Temperature rise: ΔT = PD × θJA
Junction temperature: TJ = TA + ΔT
Load regulation: ((VNL − VFL) / VFL) × 100
Ripple estimate: VOUT,ripple = VIN,ripple × 10(−PSRR/20)
2) Adjustable Linear Regulator
Output set equation: VOUT = VREF × (1 + R2/R1) + IADJ × R2
Solve for R2: R2 = (VOUT − VREF) / (VREF/R1 + IADJ)
Divider current: IDIV = VREF/R1 + IADJ
3) Zener Shunt Regulator
Series current: IS = (VIN − VZ) / RS
Zener current: IZ = IS − ILOAD
Zener power: PZ = VZ × IZ
Series resistor power: PR = IS2 × RS
Recommended series resistor: RS,req = (VIN − VZ) / (ILOAD + IZ,min)
How to Use This Calculator
- Select the regulator model: fixed linear, adjustable linear, or zener shunt.
- Enter source voltage, required output, expected load current, and thermal conditions.
- For adjustable mode, add reference voltage, adjust current, and R1 so the page can compute R2.
- For zener mode, provide source voltage, zener voltage, series resistor, load current, and sustaining zener current.
- Press the calculate button to show results above the form, inspect the graph, then download CSV or PDF if needed.
FAQs
1) What does dropout voltage mean here?
Dropout voltage is the minimum voltage difference the regulator needs between input and output to stay in control. If input falls below output plus dropout, regulation weakens and output starts following input downward.
2) Why does a linear regulator get hot quickly?
A linear regulator burns the excess voltage as heat. The larger the gap between input and output, and the higher the load current, the more power the device must dissipate.
3) Is higher PSRR always better?
For rejecting input ripple, yes. A higher PSRR usually means less ripple reaches the output. Actual performance still depends on frequency, capacitor placement, and the regulator’s operating region.
4) Why calculate junction temperature?
Junction temperature estimates device stress. Even if electrical values look correct, excessive temperature can shorten life, trigger shutdown, or push the regulator outside its safe operating area.
5) What is load regulation?
Load regulation measures output change between no-load and full-load conditions. Smaller change means better stability. It helps compare how tightly a regulator holds voltage when current demand changes.
6) When should I use zener mode?
Zener mode is useful for simple reference clamps or low-current shunt regulation. It is usually less efficient than a series regulator, especially when load current varies widely.
7) Why is the computed adjustable resistor important?
The feedback resistor network sets the target output. Small changes in resistor value, reference voltage, or adjust current can shift the final output and alter design accuracy.
8) Can this replace a full datasheet review?
No. This is a design estimator for fast engineering checks. Final work should still verify absolute ratings, transient response, capacitor stability, package limits, and manufacturer guidance.