Instrumentationsforstærkere

Instrumentationsforstærkere, often shortened to "in-amps," are a type of differential amplifier with very high common-mode rejection. They are designed to amplify small differential signals while rejecting larger common-mode signals, which are signals present on both inputs equally. This makes them ideal for amplifying signals from sensors where the desired signal is often much smaller than interference picked up by the wiring.

The core of an instrumentation amplifier typically consists of three operational amplifiers. Two buffer amplifiers, one connected to each input terminal, provide high input impedance. The output of these buffers is then fed into a third operational amplifier configured as a standard differential amplifier. The gain of the in-amp is primarily determined by a single resistor, making it easy to set and adjust.

Key characteristics of instrumentation amplifiers include high input impedance, low input offset voltage, low input bias current, and high common-mode rejection ratio (CMRR). These properties ensure that the amplifier accurately amplifies the differential signal without loading the source or being affected by noise that appears on both input lines.

Applications for instrumentation amplifiers are widespread, including medical equipment (like ECG machines), industrial control systems, data acquisition systems, and audio processing. They are crucial in situations where precise amplification of low-level signals in the presence of significant noise is required. Their predictable gain and high CMRR contribute to signal integrity and measurement accuracy in various electronic circuits.