AD620 Instrumentation Amplifier Module

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C-2 , R-6 , I-4

 29.0

Product ID: 20029 SKU: mod-20029 Categories: , Tags: , , , ,

The AD620 instrumentation amplifier module provides a platform for amplification of small AC or DC signals from analog sensors, strain gauges, transducers and similar devices.

PACKAGE INCLUDES:

  • AD620 Instrumentation Amplifier Module
  • 1×4 male header strips (x2)

KEY FEATURES OF AD620 INSTRUMENTATION AMPLIFIER MODULE:

  • Adjustable gain of 1.5 to 1000x
  • Adjustable offset
  • 120kHz bandwidth (gain = 100x)
  • Input signal range of 100uV – 300mV
  • Maximum output range of Vin – 2V
  • 3.5-10V operation (Vin)

The AD620 instrumentation amplifier module is handy for amplifying small AC or DC signals.

Module Power

AD620 Instrumentation Amplifier Module Schematic

AD620 Instrumentation Amplifier Module Reverse Engineered Schematic

The module can be powered from 3.5 to 10V on the VIN pin and adjacent GND pin.

The VIN voltage passes through a 10 ohm resistor and connects to the +Vs pin on the AD620.  We denote this as V+ on our reverse engineered schematic.

The 7660 voltage converter (charge pump) IC also takes in the V+ voltage and generates a negative voltage for the -Vs pin on the AD620 which we labeled as V-.  This gives the AD620 both positive and negative power rails.   V+ and V- also power the LM358 Op Amp

The negative voltage is also brought out to the pin labeled V- on the output side of the board in case you want to tap into it.  Do not connect this V- pin to ground or another voltage or the 7660 will be damaged.

Module Amplification / Gain

The module accepts an AC or DC input signal of between 100uV and 300mV.  The signal is input on the S+ and S- pins.

If the input is a ground referenced (single-ended) signal, the signal is connected to S+ and signal ground is connected to S-.  Alternatively, a differential signal such as from a bridge sensor can be input across the S+ and S- pins.

The inputs have a 1K series resistor to limit input current to a safe level.

Gain of the AD620 is adjusted using a 100K potentiometer (marked 104).  The advertised gain is 1.5x to 1000x and a lower resistance equals a higher gain.  Turning the pot CW increases the gain.

The output of the AD620 is passed through one of the two LM358 op amps configured as a unity gain buffer.  The LM358 can source about 30mA and sink 20mA.  The output of this buffer is available on the pin labeled VOUT.

Zero Offset Adjustment

The other half of the LM358 is also setup as a unity gain buffer to feed the Vref input of the AD620.

The input of the LM358 has a 10K potentiometer (marked 103) and series 1K resistor tied between the V+ and V- power rails.  The potentiometer adjusts the voltage input to the LM358 and the output is fed into the Vref pin on the AD620.  This allows any offset to be adjusted out or if desired, a positive or negative offset can be adjusted in.  Turning the potentiometer CW increases the offset in a positive direction.

To set the offset, the S+ and S- pins are shorted together and the 10K zero offset potentiometer is adjusted until the voltage at VOUT measures 0V or the desired amount of offset.

Module Connections

The module has inputs on one end and outputs on the other.  These can be used to connect wires or header pins can be soldered in depending on the application.

1×4 Input Header

  • VIN = Module power (3.5 to 10V)
  • GND = Ground for module power
  • S- = Signal Input (negative connection)
  • S+ = Signal Input (positive connection)

1×4 Output Header

  • V- = Negative voltage output from 7660
  • GND = Ground
  • VOUT = Signal Output
  • GND = Ground

The diagrams below show the basic connection setups for single-ended and differential inputs as well as the setup for adjusting the Zero Offset.

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