Instrumentation Amplifier Gain Calculator
Rg for any gain (or gain from Rg) — INA128/AD620-style 49.4 kΩ equation and discrete 3-op-amp designs.
The in-amp's magic is common-mode rejection, and Rg does NOT affect it — but source impedance imbalance does. Keep both inputs DC-biased (a floating thermocouple WILL rail the output). Rg's tempco adds directly to gain drift: use a 25 ppm/°C part for bridge/load-cell work, and gains above ~500 eat bandwidth (GBW/G).
Instrumentation Amp Gain Calculator computes the gain-set resistor (or the gain) of an instrumentation amplifier — free, instant and private in your browser. Sensor-interface designers amplifying small differential signals over common-mode noise use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Instrumentation Amplifier Gain Calculator
Instrumentation Amp Gain Calculator computes the gain-set resistor (or the gain) of an instrumentation amplifier using the standard engineering relation: G = 1 + 49.4 kΩ/Rg for INA128/AD620-class parts; G = 1 + 2R/Rg for discrete 3-op-amp. Worked live: Rg = 499 Ω turns an INA128 into a ×100 amplifier for load cells and thermocouples. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Instrumentation Amplifier Gain Calculator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Instrumentation Amplifier Gain Calculator?
- ✓Implements the real formula — G = 1 + 49.4 kΩ/Rg for INA128/AD620-class parts — with the substitution shown, not a black box
- ✓Built for sensor-interface designers amplifying small differential signals over common-mode noise
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate instrumentation amp gain?+
The gain-set resistor (or the gain) of an instrumentation amplifier follows G = 1 + 49.4 kΩ/Rg for INA128/AD620-class parts; G = 1 + 2R/Rg for discrete 3-op-amp. For example, Rg = 499 Ω turns an INA128 into a ×100 amplifier for load cells and thermocouples. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Why use an in-amp instead of a plain op-amp difference circuit?+
Common-mode rejection with high input impedance: a discrete difference amp needs 0.01 % matched resistors to reach 80 dB CMRR and loads the source; a monolithic in-amp delivers 100+ dB with one external resistor and gigaohm inputs.
My in-amp output sits at the rail with nothing connected — why?+
Floating inputs: bias currents need a DC path to ground on BOTH inputs. A thermocouple or AC-coupled source without reference resistors charges the inputs until something saturates. 1–10 MΩ from each input to reference fixes it without hurting the measurement.
Is the Instrumentation Amp Gain Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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