In sensor technology, accurate signal conditioning is essential for reliable data analysis. Amplification, phase control, and noise reduction are key aspects of this process. This application note explores five basic amplifier circuits at the heart of sensor signal conditioning. From inverting and non-inverting amplifiers to precision instrumentation amplifiers and versatile difference amplifiers, each circuit uniquely enhances sensor data.

The inverting amplifier is a basic circuit in sensor signal conditioning that employs an operational amplifier and a feedback network. Its operation revolves around two key aspects: signal inversion and amplification. The input signal from the sensor is connected to the inverting (-) input of the operational amplifier. The degree of amplification is determined by the ratio of the feedback resistor (RF) to the gain resistor (RG). This setup produces an output signal that is an inverted (180-degree phase-shifted) version of the input signal. Inverting amplifiers are essential when both signal amplification and inversion are required, which is common when dealing with sensors that produce signals of different polarities.

The non-inverting amplifier is another important component in sensor signal conditioning that is based on an operational amplifier and feedback resistors. It is separated from the inverting amplifier by maintaining the phase and polarity of the input signal. The input signal from the sensor is applied to the non-inverting (+) terminal of the op amp. The degree of amplification is determined by the relationship between the feedback resistor (RF) and the gain resistor (RG). Unlike the inverting amplifier, the non-inverting amplifier maintains the original phase of the input signal while amplifying. It is suitable for applications that require signal amplification without inversion, which is essential to maintain the signal phase of the sensor.

The difference amplifier, commonly called a subtractor or differential amplifier, is essential in sensor signal conditioning and is used to measure the voltage difference between two input signals. These circuits are based on the operational amplifier and excel in providing precise differential measurements. The two sensor input signals are connected to the amplifier in different ways to form a contrast. The gain of the difference amplifier is closely related to the ratio of the feedback resistor (RF) to the gain resistor (Rc). Typically, unity gain is used for high-precision differential measurements. Difference amplifiers are essential in applications that require accurate amplification and comparison of two sensor outputs, which is common in cases involving strain gages and bridge sensors.