AD620 Voltage Amplifier - Instrumentation Module, Gain 1-10000

Product overview

• Instrumentation amplifier for small voltages, measuring range ±325 mV to ±2.5 V in four selectable voltage ranges
• Integrated IC with a fixed gain or programmable gain via external resistors
• Supply voltage ±2.7 V to ±18 V or single-supply 5.4 V to 36 V
• Output voltage from 0 to +Vcc with single-supply or ±Vout with dual-supply operation
• Gain set by a resistor between pin 16 and pin 17; gain between 1 and 10000 is possible
• Internal reference voltage output (2.5 V) can be used to calibrate measured values

Product description

The AD620 is a signal amplifier for measuring very small voltages, such as those supplied by sensors or measurement interfaces. The integrated instrumentation amplifier operates differentially: it detects the voltage difference between two inputs and amplifies only that difference, while suppressing interference on both lines (so-called common-mode noise). This makes the module ideal for applications in which signals are transmitted over longer cables or multiple sources of interference are present in the surroundings.

The gain is controlled by the value of an external resistor; the internal circuit then calculates the exact gain. A 100 kOhm resistor results in a gain of 100, while a 1-kOhm resistor results in a gain of 10000. The internal 2.5 V reference voltage enables feedback to the sensor, for example to supply a measuring transducer. The output is interpreted differently depending on the power supply (single-supply or dual-supply) and requires appropriate evaluation by analog-to-digital converters or similar circuits.

The amplifier is suitable for load cells and pressure sensors in weighing systems, humidity or temperature sensors using low-resistance measuring bridges, and biomedical sensors such as those used for ECG measurements. It is also frequently used in laboratory setups to make weak signals visible before they are digitized. A particular advantage is its relatively high input resistance, which places very little load on sensors.

The supply voltage is selected according to the project requirements. For battery operation, ±2.7 V is sufficient; in the laboratory, ±18 V is possible with laboratory power supplies. The output must be evaluated using an analog-to-digital converter or a measurement module with a suitable input voltage. Achieving an exact gain requires calculating or measuring the external resistor, and calibration may be necessary if the highest accuracy is required.

Safety notice

The module is intended exclusively for building prototypes and for testing and development purposes. It is not suitable for installation in household mains circuits. When working on or near electrical installations, consult a qualified electrician; if in doubt, consult a qualified electrician before commissioning.

Scope of delivery

• 1x AD620 voltage amplifier signal instrumentation module