Instrumentierungsverstärkern

Instrumentierungsverstärker, often abbreviated as "Inst-Amp", are a type of differential amplifier that excels at amplifying small signals in the presence of large noise voltages. Their primary characteristic is their high common-mode rejection ratio (CMRR), meaning they can effectively suppress signals that are common to both input terminals while amplifying the difference between them. This makes them ideal for applications where low-level signals need to be measured accurately, even in electrically noisy environments.

Unlike a standard op-amp configured as a differential amplifier, instrumentierungsverstärker typically have three op-amps. Two of these op-amps buffer the input signals, providing high input impedance. This prevents the amplifier from loading the signal source, which is crucial when dealing with high-impedance sensors. The third op-amp then performs the differential amplification. The gain of an instrumentierungsverstärker is usually set by a single external resistor, simplifying circuit design and adjustment.

Key features of instrumentierungsverstärker include their high input impedance, low input bias currents, high CMRR, and precise, easily adjustable gain. These properties make them indispensable in a wide range of applications, such as medical instrumentation (e.g., ECG and EEG amplifiers), industrial process control, data acquisition systems, and audio preamplifiers. They are particularly useful for amplifying signals from bridge sensors, thermocouples, and strain gauges, where the desired signal is often small and differential, and the surrounding environment may be noisy.