Each Alternative Details

INA129 – Texas Instruments

The closest functional match to AD620 in the TI lineup. Same 8-pin package, same pinout, and crucially INA129 uses the same gain equation as AD620 — G = 1 + (49.4k / RG) — so your existing gain resistor value carries over directly. No layout change, no gain resistor recalculation. Lower quiescent current at 700uA vs AD620’s 1.3mA, useful in battery-powered designs. If your application is a direct board replacement and you want supply chain diversity away from Analog Devices, INA129 is the answer.

Pin compatible: Yes. Layout change: No. Gain resistor change: No. Firmware change: No.

AD623 – Analog Devices

Same pinout as AD620 and adds single-supply operation — it runs from a single 3V to 12V rail or dual supply. If your board originally runs on dual supply and you are not switching to single supply, it swaps in directly. If you are redesigning for single-supply, AD623 is the natural path. Gain range tops out at 1,000 rather than 10,000, so verify this against your application before committing. Noise is higher at 35 nV/Hz vs AD620’s 9 nV/Hz — for ECG and general sensor interfaces this is typically acceptable, but run the noise budget if your signal chain is tight.

Pin compatible: Yes. Layout change: No. Gain resistor change: No. Firmware change: No.

INA128 – Texas Instruments

Same 8-pin DIP and SO-8 package as AD620, same noise performance at 8 nV/Hz, same 120dB CMRR. The one detail to watch: INA128 uses a slightly different gain equation — G = 1 + (50k / RG) — while AD620 and INA129 use G = 1 + (49.4k / RG). The difference is small at low gain values but becomes meaningful at high gain. At G = 100 for example, AD620 needs RG = 499 ohms while INA128 needs RG = 505 ohms. Recalculate your RG value before swapping. If you can accept that one step, INA128 gives you equivalent performance with full TI supply chain support.

Pin compatible: Yes. Layout change: No. Gain resistor change: Yes (recalculate RG using G = 1 + (50k / RG)). Firmware change: No.

AD8226 – Analog Devices

Not pin-compatible with AD620 — AD8226 uses a different pinout and requires a layout change. The reason to use it is single-supply operation from as low as 2.2V, which covers 3.3V and 5V single-supply systems, combined with rail-to-rail output. Lower quiescent current than AD620. A practical choice for portable medical devices, wearables, and battery-powered sensor nodes where supply voltage is low and every milliamp of quiescent current matters. Gain is set by the same resistor-based method: G = 1 + (80k / RG), so recalculate your RG value for the new equation.

Pin compatible: No. Layout change: Yes. Gain resistor change: Yes (recalculate RG using G = 1 + (80k / RG)). Firmware change: No.

AD8422 – Analog Devices

Third-generation development of the AD620, with meaningfully better specs: 6 nV/Hz input noise, 130dB CMRR, rail-to-rail output, and less than one-third the power consumption of AD620. Not pin-compatible with AD620 — it uses the High-Performance Pinout introduced by the AD8221, so a layout change is required. The gain equation also differs: G = 1 + (19.8k / RG). To get the same gain as your existing AD620 circuit, multiply your current RG value by 0.4008 to find the new RG for AD8422. For new designs where noise floor and CMRR are the primary constraints — precision medical equipment, high-accuracy data acquisition, load cells — AD8422 is the best-performing option on this page.

Pin compatible: No. Layout change: Yes. Gain resistor change: Yes (new RG = existing AD620 RG x 0.4008). Firmware change: No.