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8 Zero-drift Amplifiers: Features and Benefits By Errol Leon, Richard Barthel, Tamara Alani, Texas Instruments Zero-drift amplifiers employ a unique, self-correcting technology which provides ultra-low input offset voltage (VOS) and near-zero input offset voltage drift over time and temperature (dVOS/dT) suitable for general and precision applications. TI's zero-drift topology also delivers other advantages including no 1/f noise, low broadband noise, and low distortion simplifying development complexity and reducing cost. This may be done 1 of 2 ways: Chopper or auto-zeroing. This tech note will explain the differences between standard continuous- time and zero-drift amplifiers. Applications suitable for zero-drift amplifiers Zero-drift amplifiers are suitable for a wide variety of general- purpose and precision applications that benefit from stability in the signal path. The excellent offset and drift performance of these amplifiers make it especially useful early in the signal path, where high gain configurations and interfacing with micro-volt signals are common. Common applications that benefit from this technology include precision strain gauge and weight scales, current shunt measurement, thermocouple-, thermopile-, and bridge-sensor interfaces. Rail-to-rail zero-drift amplifiers System performance can be optimized by using standard continuous-time amplifiers plus a system level auto-calibration mechanism. However, this additional auto-calibration requires complicated hardware and software which results in increased development time, cost, and board space. The alternative and more efficient solution is to use a zero-drift amplifier, such as the OPA388. A traditional rail-to-rail input CMOS architecture has two differential pairs; one PMOS transistor pair (blue) and one NMOS transistor pair (red). Zero-drift amplifiers with rail-to-rail input operation use the same complementary p-channel (blue) and n-channel (red) input configuration shown below in Figure 1. The result of this input architecture exhibits some degree of crossover distortion (for more information on crossover Figure 1: Simplified PMOS / NMOS Differential Pair