Op-Amp Gain Calculator
Gain of an op-amp stage in both configurations, in ratio and decibels, with the output and the bandwidth left.
Results
What this tool does
Both configurations use the same two resistors, but the non-inverting one can never go below a gain of one, while the inverting one can attenuate and flips the signal upside down. The inverting arrangement also loads the source with the input resistor, which the non-inverting one does not — often the real reason to choose between them.
Formula
non-inverting: G = 1 + Rf ÷ Rin ; inverting: G = − Rf ÷ Rin
Variables
| Symbol | Meaning | Unit |
|---|---|---|
rf | Feedback resistance | kΩ |
ri | Input resistance | kΩ |
vi | Input voltage | V |
gb | Gain-bandwidth product | MHz |
GN | Gain | — |
GI | Gain | — |
DB | Gain in decibels | dB |
VO | Output voltage | V |
BW | Usable bandwidth | kHz |
Worked example
- Feedback resistance100 kΩ
- Input resistance10 kΩ
- Input voltage0.1 V
- Gain-bandwidth product1 MHz
- Gain11.00000
- Gain-10.00000
- Gain in decibels20.82785 dB
- Output voltage1.10000 V
- Usable bandwidth90.909 kHz
Limitations
- Electrical installations are governed by national wiring rules. Cable sizing also depends on installation method, grouping, ambient temperature and protection devices, which this calculator does not evaluate.
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.
- Coverage and consumption figures vary between products. Take the values from the manufacturer's datasheet for the product you are actually using.
Frequently asked questions
Why does more gain mean less bandwidth?
Because an op-amp has a fixed gain-bandwidth product: whatever gain you ask for, the frequency at which it runs out is that product divided by the gain. A part rated at 1 MHz gives a megahertz of bandwidth at unity gain, but only 91 kHz at a gain of eleven. When one stage cannot give both, the usual answer is two stages of lower gain in series, whose bandwidths multiply far more kindly.