OPA129

OPA129 OPA129 OPA129 SBOS026A – JANUARY 1994 – REVISED APRIL 2007 Ultra-Low Bias Current Difet® OPERATIONAL AMPLIFIER FEATURES q ULTRA-LOW BIAS CURRENT: 100fA max q LOW OFFSET: 2mV max q LOW DRIFT: 10µV/°C max q HIGH OPEN-LOOP GAIN: 94dB min q LOW NOISE: 15nV/√Hz at 10kHz q PLASTIC DIP AND SO PACKAGES DESCRIPTION The OPA129 is an ultra-low bias current monolithic operational amplifier offered in an 8-pin PDIP and SO-8 package. Using advanced geometry dielectrically-isolated FET (Difet®) inputs, this monolithic amplifier achieves a high performance level. Difet fabrication eliminates isolation-junction leakage current—the main contributor to input bias current with conventional monolithic FETs. This reduces input bias current by a factor of 10 to 100. Very low input bias current can be achieved without resorting to small-geometry FETs or CMOS designs which can suffer from much larger offset voltage, voltage noise, drift, and poor power-supply rejection. The OPA129 special pinout eliminates leakage current that occurs with other op amps. Pins 1 and 4 have no internal connection, allowing circuit board guard traces— even with the surface-mount package version. OPA129 is available in 8-pin DIP and SO packages, specified for operation from –40°C to +85°C. APPLICATIONS q PHOTODETECTOR PREAMPS q CHROMATOGRAPHY q ELECTROMETER AMPLIFIERS q MASS SPECTROMETERS q pH PROBE AMPLIFIERS q ION GAGE MEASUREMENT –In 2 3 +In Noise-Free Cascode 30kΩ 30kΩ Simplified Circuit Substrate 8 7 ...