op amp amplifier calculator - Aaron Graves, PhDude Replica

Op-Amp Gain & Output Voltage Calculator

Calculate closed-loop gain and output voltage for common op amp topologies. This tool also checks whether the output clips at your supply rails.

Amplifier Type

Input Voltage Vin (V)

R1 (Rg to ground, Ω)

Rf (feedback resistor, Ω)

Reference Voltage Vref (V)

Positive Supply Rail V+ (V)

Negative Supply Rail V− (V)

Tip: For single-supply circuits, try V+ = 5 and V− = 0.

Enter values and click Calculate.

What this op amp amplifier calculator does

This calculator helps you quickly estimate gain and output voltage for three of the most common op-amp configurations: non-inverting amplifier, inverting amplifier, and voltage follower. It is designed for fast bench work, homework checks, and early-stage analog design planning.

Along with ideal output voltage, the tool compares your result to the power rails you entered and reports clipping when the op amp is being asked to swing beyond what the supply allows.

Core equations used

1) Non-inverting amplifier

Gain Av = 1 + (Rf / Rg)

Vout = Vref + Av × (Vin − Vref)

2) Inverting amplifier

Gain Av = −(Rf / Rin)

Vout = Vref × (1 + Rf/Rin) − (Rf/Rin) × Vin

3) Voltage follower

Gain Av = 1

Vout = Vin

How to use the calculator

Select the amplifier type.
Enter input voltage and resistor values (if required by topology).
Set reference voltage (usually 0 V in dual-supply circuits, or mid-supply in single-supply designs).
Enter your positive and negative supply rails.
Click Calculate to see gain, ideal output, and clipped output.

Example design checks

Example A: Non-inverting gain of 10

Let Rg = 2 kΩ and Rf = 18 kΩ. Gain is 1 + 18k/2k = 10. If Vin = 0.2 V and Vref = 0, ideal output is 2.0 V. With ±12 V rails, no clipping occurs.

Example B: Inverting gain of -4 on a 5 V single supply

Let Rin = 10 kΩ and Rf = 40 kΩ, so gain is -4. If Vin = 0.8 V and Vref = 2.5 V (biased midpoint), calculate output. If the ideal value exceeds 0 V to 5 V, the circuit clips and distortion will occur.

Practical design advice

Choose resistor values thoughtfully

Common starting range: 1 kΩ to 100 kΩ.
Very low values increase current draw.
Very high values can increase noise and bias-current errors.

Remember real op amp limits

Output swing is usually not exactly equal to supply rails (unless rail-to-rail and lightly loaded).
Gain-bandwidth product limits high-frequency performance.
Slew rate can distort fast-changing signals.
Input common-mode range must include your signal range.

When this calculator is most useful

This calculator is ideal for quick first-pass analysis. Use it to sanity-check resistor ratios, confirm polarity, and estimate whether clipping is likely. For final verification, run a SPICE simulation and validate against your op amp datasheet under expected load and temperature conditions.

Quick troubleshooting checklist

If your output is stuck near a rail, check for clipping and common-mode violations.
If gain is wrong, verify resistor placement and actual measured resistor values.
If noise is high, lower impedance levels and improve grounding/decoupling.
If response is unstable, verify phase margin and compensation requirements.