概要

The AD627 is an integrated, micropower instrumentation amplifier that delivers rail-to-rail output swing on single and dual (+2.2 V to ±18 V) supplies. The AD627 provides excellent ac and dc specifications while operating at only 85 μA maximum.
The AD627 offers superior flexibility by allowing the user to set the gain of the device with a single external resistor while conforming to the 8-lead industry-standard pinout configuration. With no external resistor, the AD627 is configured for a gain of 5. With an external resistor, it can be set to a gain of up to 1000.
A wide supply voltage range (+2.2 V to ±18 V) and micropower current consumption make the AD627 a perfect fit for a wide range of applications. Single-supply operation, low power consumption, and rail-to-rail output swing make the AD627 ideal for battery-powered applications. Its rail-to-rail output stage maximizes dynamic range when operating from low supply voltages. Dual-supply operation (±15 V) and low power consumption make the AD627 ideal for industrial applications, including 4 mA to 20 mA loop-powered systems.
The AD627 does not compromise performance, unlike other micropower instrumentation amplifiers. Low voltage offset, offset drift, gain error, and gain drift minimize errors in the system. The AD627 also minimizes errors over frequency by providing excellent CMRR over frequency. Because the CMRR remains high up to 200 Hz, line noise and line harmonics are rejected.
The AD627 provides superior performance, uses less circuit board area, and costs less than micropower discrete designs.

 

特徴

Micropower, 85 μA maximum supply current
Wide power supply range (+2.2 V to ±18 V)
Easy to use
-Gain set with one external resistor
-Gain range 5 (no resistor) to 1000
Higher performance than discrete designs
Rail-to-rail output swing
High accuracy dc performance
-0.03% typical gain accuracy (G = +5) (AD627A)
-10 ppm/°C typical gain drift (G = +5)
-125 μV maximum input offset voltage (AD627B dual supply)
-200 μV maximum input offset voltage (AD627A dual supply)
-1 μV/°C maximum input offset voltage drift (AD627B)
-3 μV/°C maximum input offset voltage drift (AD627A)
-10 nA maximum input bias current
Noise: 38 nV/√Hz RTI noise at 1 kHz (G = +100)
優れた交流仕様
-AD627A: 77 dB minimum CMRR (G = +5)
-AD627B: 83 dB minimum CMRR (G = +5)
-80 kHz bandwidth (G = +5)
-135 μs settling time to 0.01% (G = +5, 5 V step)

 

アプリケーション

4 mA to 20 mA loop-powered applications
Low power medical instrumentation—ECG, EEG
Transducer interfacing
熱電対アンプ
工業プロセス制御
Low power data acquisition
Portable battery-powered instruments

 

動作理論

The AD627 is a true instrumentation amplifier, built using two feedback loops. Its general properties are similar to those of the classic two-op-amp instrumentation amplifier configuration but internally the details are somewhat different. The AD627 uses a modified current feedback scheme, which, coupled with interstage feedforward frequency compensation, results in a much better common-mode rejection ratio (CMRR) at frequencies above dc (notably the line frequency of 50 Hz to 60 Hz) than might otherwise be expected of a low power instrumentation amplifier.

 

リファレンス端子

The reference terminal potential defines the zero output voltage and is especially useful when the load does not share a precise ground with the rest of the system. It provides a direct means of injecting a precise offset to the output. The reference terminal is also useful when amplifying bipolar signals, because it provides a virtual ground voltage.
The AD627 output voltage is developed with respect to the potential on the reference terminal; therefore, tying the REF pin to the appropriate local ground solves many grounding problems. For optimal CMR, tie the REF pin to a low impedance point.