# AD620

**Analog Devices** · Instrumentation Amplifier · SOIC-8

The AD620 is a low-power, low-noise instrumentation amplifier that sets gain (1 to 1000) with a single external resistor. Its high common-mode rejection, low input bias current, and low noise make it a long-standing choice for amplifying small differential signals from bridge sensors, thermocouples, and biopotential measurements like ECG.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | RG | passive | Gain-setting resistor terminal. Connect an external resistor RG between pins 1 and 8 to program the gain: G = 1 + (49.4 kΩ / RG). Leave open for unity gain (G = 1). |
| 2 | -IN | input | Inverting analog input of the instrumentation amplifier. Differential input impedance 10 GΩ||2 pF; input voltage range within (-Vs + 1.9 V) to (+Vs - 1.2 V) at ±15 V supply. |
| 3 | +IN | input | Noninverting analog input of the instrumentation amplifier. Differential input impedance 10 GΩ||2 pF; input voltage range within (-Vs + 1.9 V) to (+Vs - 1.2 V) at ±15 V supply. |
| 4 | -VS | power_in | Negative supply rail. Operating range ±2.3 V to ±18 V (bipolar) referenced to +VS. Quiescent current 0.9 mA typ, 1.3 mA max. |
| 5 | REF | input | Reference input. Sets the DC level of the output; the output voltage is measured with respect to this pin. Input resistance 20 kΩ typical, input current 50 µA (60 µA max) when VIN+ = VREF = 0. Must be driven from a low-impedance source to preserve CMRR. |
| 6 | OUTPUT | output | Amplifier output. Output voltage = G × (V+IN - V-IN) + VREF. Output swing to within ~1.2 V of the rails at ±15 V into 10 kΩ; short-circuit current ±18 mA. |
| 7 | +VS | power_in | Positive supply rail. Operating range ±2.3 V to ±18 V (bipolar). Quiescent current 0.9 mA typ, 1.3 mA max. |
| 8 | RG | passive | Gain-setting resistor terminal. Connect an external resistor RG between pins 1 and 8 to program the gain: G = 1 + (49.4 kΩ / RG). Leave open for unity gain (G = 1). |

## Key specifications

| Parameter | Value |
|---|---|
| Type | Instrumentation amplifier |
| Gain | 1 to 1000 (single external resistor) |
| Input offset voltage | 50 uV max |
| Input noise | 9 nV/sqrt(Hz) at 1 kHz |
| CMRR | 100 dB min (G >= 10) |
| Supply voltage | +-2.3 V to +-18 V |
| Supply current | 1.3 mA max |
| Operating temperature | -40 C to 85 C |

## Ordering variants

- `AD620AR`
- `AD620ARZ`
- `AD620AR-REEL`
- `AD620ARZ-REEL`
- `AD620AR-REEL7`
- `AD620ARZ-REEL7`
- `AD620BR`
- `AD620BRZ`
- `AD620BR-REEL`
- `AD620BRZ-RL`
- `AD620BR-REEL7`
- `AD620BRZ-R7`
- `AD620AN`
- `AD620ANZ`
- `AD620BN`
- `AD620BNZ`
- `AD620SQ/883B`

## CAD (KiCad official)

- Symbol: `ad620.kicad_sym`
- Footprint: `ad620.kicad_mod`
- 3D model: SOIC-8 body from KiCad `Package_SO/SOIC-8_3.9x4.9mm_P1.27mm`.
- 3D model files: `ad620-etched.step` / `ad620-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `ad620.step` / `ad620.glb` are the bare package body.

## Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

- **Datasheet:** [Analog Devices datasheet](https://www.analog.com/media/en/technical-documentation/data-sheets/AD620.pdf) (20 pp, sha256 `83d076a7bf5e92d3`, retrieved 2026-08-17, tier: manufacturer)
- **Extractor:** `ds2sf` (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/ad620-datasheet.pdf)