Nearest E24 value: 100 kΩ
What Is a Non-Inverting Op Amp?
A non-inverting operational amplifier is the second fundamental op-amp configuration in analog electronics. The input signal drives the non-inverting (+) input directly, while a voltage divider formed by the feedback resistor Rf and the ground resistor Rin returns a fraction of the output to the inverting (−) input. Negative feedback forces the inverting input to track the input voltage, so the closed-loop gain depends only on the two resistors. The output is an amplified, in-phase copy of the input — no polarity flip — and the input impedance is extremely high because the signal sees only the op amp’s own input.
How to Use This Calculator
1. Set the ground resistor (Rin) — the resistor from the inverting (−) input to ground. 2. Set the feedback resistor (Rf) — from the output back to the inverting input; set it to 0 for a unity-gain voltage follower. 3. Enter your input signal peak and supply rails. The gain, gain in dB and output voltage update instantly, the circuit relabels itself, and the waveform redraws — including clipping if the output would exceed the rails. 4. Designing to a target gain? Use the Reverse Design box: enter the gain you need and it returns Rf = (Av−1)×Rin plus the nearest standard E24 resistor and its gain error.
Non-Inverting Amplifier Gain Formula
Av = 1 + Rf / Rin
Vout = (1 + Rf / Rin) × Vin
Gain (dB) = 20 × log10(Av)
Where Rf is the feedback resistor and Rin is the resistor from the inverting input to ground. Because the ratio Rf/Rin can never be negative, the minimum gain is exactly +1 — the voltage follower. The output stays in phase with the input (0° phase shift), and the input impedance is very high (typically MΩ to GΩ), which is the main advantage over the inverting configuration.
Calculate the Feedback Resistor (Reverse Design)
Design work usually starts from the gain you need. Rearranging the formula to calculate the feedback resistor:
Rf = (Av − 1) × Rin
Need a gain of +21 with Rin = 1 kΩ? Then Rf = 20 × 1 k = 20 kΩ — already a standard E24 value. Need +15 with Rin = 2.2 kΩ? Rf = 14 × 2.2 k = 30.8 kΩ, nearest E24 is 30 kΩ (gain +14.6, about 2.4% low). The Reverse Design box does this E24 rounding automatically and reports the exact gain error.
Worked Examples
Example 1 — Gain of +11 (the classic 1 kΩ / 10 kΩ pair)
Rin = 1 kΩ, Rf = 10 kΩ, Vin = 0.5 V peak.
Av = 1 + 10k/1k = +11 (20.8 dB). Vout = 11 × 0.5 V = +5.5 V peak, in phase. With ±12 V rails (saturation ≈ ±10.5 V) the amplifier stays linear. Note how the same resistor pair gives −10 in the inverting topology but +11 here.
Example 2 — Clipping at the rails
Same resistors, but Vin = 1.2 V peak. Ideal output = +13.2 V, yet the op amp can only swing to about ±10.5 V on ±12 V supplies. The waveform clips flat at +10.5 V — try it in the calculator and watch the orange trace flatten.
Example 3 — Voltage follower (unity-gain buffer)
Set Rf = 0: Av = 1 + 0 = +1 exactly. The output copies the input while presenting near-infinite input impedance and near-zero output impedance — the standard way to buffer a potentiometer, sensor or high-impedance divider before driving a load or an ADC.
Quick Gain Reference Table
| Rin | Rf | Gain Av | Gain (dB) |
|---|---|---|---|
| any | 0 Ω | +1 | 0 dB (voltage follower) |
| 10 kΩ | 10 kΩ | +2 | 6.0 dB |
| 10 kΩ | 47 kΩ | +5.7 | 15.1 dB |
| 1 kΩ | 10 kΩ | +11 | 20.8 dB |
| 1 kΩ | 99 kΩ | +100 | 40 dB |
| 1 kΩ | 100 kΩ | +101 | 40.1 dB |
Non-Inverting vs Inverting Amplifier
| Property | Non-Inverting | Inverting |
|---|---|---|
| Gain formula | 1 + Rf/Rin | −Rf/Rin |
| Phase | In phase (0°) | 180° inverted |
| Input impedance | Very high (MΩ–GΩ) | ≈ Rin (low–moderate) |
| Minimum gain | +1 (cannot attenuate) | Below 1 possible |
| Typical uses | Buffers, sensor front-ends, high-Z sources | Summing mixers, filters, transimpedance |
Need the inverted counterpart? Use the companion Inverting Op Amp Gain Calculator, which adds a 180° phase flip and lets the gain drop below unity.
Need a current output instead of a voltage? See the Op-Amp Voltage to Current Converter Calculator — a voltage-controlled current source with compliance-limit modeling.
Design Tips for Real Circuits
1. Choose sensible resistor values. Keep Rin and Rf in the 1 kΩ–1 MΩ range: too low loads the op amp output through the feedback divider; too high adds noise and bias-current error. 2. Watch the gain-bandwidth product. Closed-loop bandwidth ≈ GBW ÷ Av. A 1 MHz-GBW op amp at gain +100 leaves ~10 kHz; an NE5532 (10 MHz) still covers the audio band (~100 kHz). 3. Respect the rails. Classic op amps saturate roughly 1.5 V below each supply; this calculator clips at ±(VCC − 1.5 V) so you see the real limit. 4. Buffer tricky sources first. When a sensor cannot drive Rin of an inverting stage, put a non-inverting buffer (Rf = 0) in front — its huge input impedance solves the loading problem.
Where Non-Inverting Amplifiers Are Used
Anywhere the source must not be loaded: sensor front-ends (thermocouples, pH probes, piezo pickups), voltage followers buffering potentiometers and references, audio preamps after high-impedance microphones, and ADC drivers presenting a low output impedance to the converter — size the conversion chain with our ADC Calculator. Working in dB? The Attenuation Calculator converts ratios both ways, and resistor basics live in the Ohm’s Law and Series Resistor calculators.
Frequently Asked Questions
What is the gain formula for a non-inverting op amp?
The closed-loop voltage gain is Av = 1 + Rf / Rin. The output is in phase with the input. With Rf = 10 kΩ and Rin = 1 kΩ the gain is +11: a 0.5 V input produces a 5.5 V output.
Why is the minimum gain of a non-inverting amplifier +1?
Because the gain is 1 + Rf/Rin and a resistor ratio can never be negative, the smallest possible gain is exactly 1 (Rf = 0). To attenuate a signal you need the inverting topology or a divider in front.
What is a voltage follower (unity gain buffer)?
A non-inverting amplifier with Rf = 0 — the output wired straight to the inverting input. Gain is exactly +1, input impedance extremely high, output impedance near zero. It isolates weak, high-impedance sources from whatever load follows.
What happens when the output hits the supply rails?
A real op amp cannot swing beyond its supplies. If (1 + Rf/Rin)×Vin exceeds the saturation limit (≈ VCC − 1.5 V for classic parts), the output clips flat at the rail — visible live in the waveform above.
What is the input impedance of a non-inverting amplifier?
Extremely high — typically MΩ to GΩ — because the signal drives the op amp’s non-inverting input directly and feedback bootstraps it even higher. This is the key advantage over the inverting topology, whose input impedance is only Rin.
Can I use this calculator for real-world circuit design?
Yes — it gives the ideal closed-loop gain the resistors set. In hardware, expect small deviations from resistor tolerance (1% parts → ~2% worst-case gain error), finite gain-bandwidth at high frequency, and bias effects in precision work. The Reverse Design box rounds to standard E24 values and reports the resulting gain error.
What is the difference between inverting and non-inverting gain?
Non-inverting: Av = 1 + Rf/Rin, in phase, very high input impedance, minimum gain +1. Inverting: Av = −Rf/Rin, 180° phase flip, input impedance ≈ Rin, gain below 1 possible. Full comparison table above.