JFET Input Instrumentation Amplifier with Rail-to-Rail Output in MSOP Package

The AD8220 is the first single-supply, JFET input instrumentation amplifier available in an MSOP package. Designed to meet the needs of high performance, portable instrumentation, the AD8220 has a minimum common-mode rejection ratio (CMRR) of 86 dB at dc and a minimum CMRR of 80 dB at 5 kHz for G = 1. Maximum input bias current is 10 pA and typically remains below 300 pA over the entire industrial temperature range. Despite the JFET inputs, the AD8220 typically has a noise corner of only 10 Hz.

With the proliferation of mixed-signal processing, the number of power supplies required in each system has grown. The AD8220 is designed to alleviate this problem. The AD8220 can operate on a ±18 V dual supply, as well as on a single +5 V supply. Its rail-to-rail output stage maximizes dynamic range on the low voltage supplies common in portable applications. Its ability to run on a single 5 V supply eliminates the need to use higher voltage, dual supplies. The AD8220 draws a maximum of 750 μA of quiescent current, making it ideal for battery powered devices.

Gain is set from 1 to 1000 with a single resistor. Increasing the gain increases the common-mode rejection. Measurements that need higher CMRR when reading small signals benefit when the AD8220 is set for large gains.

A reference pin allows the user to offset the output voltage. This feature is useful when interfacing with analog-to-digital converters.

The AD8220 is available in an MSOP that takes roughly half the board area of an SOIC. Performance for the A and B grade is specified over the industrial temperature range of −40°C to +85°C, and the W grade is specified over the automotive temperature range of −40°C to +125°C.

Applications

* Medical instrumentation

* Precision data acquisition

* Transducer interfaces

* High CMRR

* 100 dB CMRR (minimum), G = 10 (B grade)

* 80 dB CMRR (minimum) to 5 kHz, G = 1 (B grade)

* Excellent ac specifications and low power

* 1.5 MHz bandwidth (G = 1)

* 14 nV/√Hz input noise (1 kHz)

* Slew rate: 2 V/μs

* 750 μA quiescent supply current (maximum)