ALLGEMEINE BESCHREIBUNG

The AD8293G80/AD8293G160 are small, low cost, precision instrumentation amplifiers that have low noise and rail-to-rail outputs. They are available in two fixed-gain models: 80 and 160. They incorporate the gain setting resistors and filter resistors, reducing the number of ancillary components. For example, only two external capacitors are needed to implement a 2-pole filter. The AD8293G80/AD8293G160 also feature low offset voltage, offset drift, and gain drift coupled with high commonmode rejection. They are capable of operating on a supply of 1.8 V to 5.5 V.
With a low offset voltage of 20 μV (AD8293G160B), an offset voltage drift of 0.3 μV/°C, and a voltage noise of only 0.7 μV p-p (0.01 Hz to 10 Hz), the AD8293G80/AD8293G160 are ideal for applications where error sources cannot be tolerated.
Precision instrumentation, position and pressure sensors, medical instrumentation, and strain gauge amplifiers benefit from the low noise, low input bias current, and high commonmode rejection. The small footprint and low cost are ideal for high volume applications.
The small package and low power consumption allow the maximum channel density and the minimum board size required for portable systems. Designed for ease of use, these instrumentation amplifiers, unlike more traditional ones, have a buffered reference, eliminating the need for an additional op amp to set the reference voltage to midsupply.
The AD8293G80/AD8293G160 are specified over the industrial temperature range from −40°C to +85°C. The AD8293G80/ AD8293G160 are available in a halogen-free, Pb-free, 8-lead SOT-23.

 

FEATURES

Small package: 8-lead SOT-23
Reduced component count Incorporates gain resistors and filter resistors
Low offset voltage: 20 μV maximum
Low offset drift: 0.3 μV/°C maximum
Low gain drift: 25 ppm/°C maximum
High CMR: 140 dB typical
Low noise: 0.7 μV p-p from 0.01 Hz to 10 Hz
Single-supply operation: 1.8 V to 5.5 V
Rail-to-rail output
Available in 2 fixed-gain models

 

ANWENDUNGEN

Current sensing
Strain gauges
Regelkreise für Laserdioden
Portable medical instruments
Thermoelement-Verstärker

 

HIGH PSR AND CMR

Common-mode rejection and power supply rejection indicate the amount that the offset voltage of an amplifier changes when its common-mode input voltage or power supply voltage changes. The autocorrection architecture of the AD8293G80/AD8293G160 continuously corrects for offset errors, including those induced by changes in input or supply voltage, resulting in exceptional rejection performance. The continuous autocorrection provides great CMR and PSR performances over the entire operating temperature range (−40°C to +85°C).
The parasitic resistance in series with R2 does not degrade CMR, but causes a small gain error and a very small offset error. Therefore, an external buffer amplifier is not required to drive VREF to maintain excellent CMR performance. This helps reduce system costs over conventional instrumentation amplifiers.

 

1/f NOISE CORRECTION

Flicker noise, also known as 1/f noise, is noise inherent in the physics of semiconductor devices and decreases 10 dB per decade. The 1/f corner frequency of an amplifier is the frequency at which the flicker noise is equal to the broadband noise of the amplifier. At lower frequencies, flicker noise dominates, causing large errors in low frequency or dc applications.
Flicker noise is seen effectively as a slowly varying offset error, which is reduced by the autocorrection topology of the AD8293G80/AD8293G160. This allows the AD8293G80/AD8293G160 to have lower noise near dc than standard low noise instrumentation amplifiers.

 

REFERENCE CONNECTION

Unlike traditional 3-op-amp instrumentation amplifiers, parasitic resistance in series with REF (Pin 3) does not degrade CMR performance. The AD8293G80/AD8293G160 can attain extremely high CMR performance without the use of an external buffer amplifier to drive the REF pin, which is required by industry standard instrumentation amplifiers. Reducing the need for buffer amplifiers to drive the REF pin helps to save valuable printed circuit board (PCB) space and minimizes system costs.