Instrument Amps Eliminate Drift

The MAX4208 and MAX4209H instrumentation amplifiers employ the company’s patented current-feedback architecture, described as a spread-spectrum auto-zeroing technique that constantly measures and corrects the input offset voltage to eliminate drift over time and temperature. Input offset voltage for both amps is 20 µV maximum at 25°C and 40 µV maximum from -40°C to +125°C. Their input stages use CMOS transistors with 1 pA input bias. The devices offer true ground sensing and an input common-mode voltage range of -1V to -1.3 V. Common-mode rejection ratio is guaranteed to be at least 106 dB. The MAX4208 features an adjustable gain set by the ratio of two external resistors (G = 1 + R2/R1). The MAX4209H uses internal laser-trimmed resistors to set a fixed gain of 100x. The MAX4209H has a maximum gain error of ±0.25% at +25°C, ±0.3% up to +85°C, and ±0.35% over the entire -40°C to +125°C range. Typical gain error is better than ±0.1%. The devices fit into a 3 mm x 5 mm microMAX package. Pricing is $1.65 each/100. MAXIM INTEGRATED PRODUCTS, Sunnyvale, CA. (800) 998-8800.