General-purpose op amps

Voltage monitoring involves tracking electrical signals to ensure a system remains within safe and specified limits. This process is essential in maintaining an efficient system by preventing damage to surrounding components and avoiding downtime. Op amps ensure accurate voltage detection across many applications, such as industrial power distribution, test and measurement, motor drives and more.

Voltage monitoring may be done across various amplifier topologies. For example, a buffer configuration may be used when measuring a voltage without drawing significant source current or loading the circuit. Alternatively, an op amp could be used as a comparator, detecting whether a monitored signal is above or below a certain voltage threshold.

Given two input voltages, an op amp may be used to amplify the difference between the two signals. Typically, some sort of resistor network is designed to subtract one signal from the other. Difference amps may be implemented in one of two ways: discretely in conjunction with external resistors and capacitors, or integrated where the entire circuit is fabricated on a single chip, offering a high degree of precision between input signals.

Applications include medical instrumentation, audio systems and data acquisition (DAQ) systems, among others. Op amps in medical devices require high gain and excellent common-mode rejection, while precision DAQ systems call for low-input offset to maintain signal integrity. 

Current sensing measures the flow of electric current in a circuit, often seeing crucial applications in motor control, battery management, and power supplies. Op amps amplify a voltage drop across a shunt resistor (current-sensing resistor), allowing an accurate voltage reading, which is proportional to current. Using known resistor values, the original current can be calculated through the output voltage.

Low-input offset voltage, low-input bias current, and the use of precision resistors are desirable for sensing current, where the op amp deals with small voltage drops. As such, a difference amplifier topology may be useful in characterizing millivolts of voltage drops across the shunt.

Active filters use op amps, in combination with resistors and capacitors, to shape the frequency response of a signal. Unlike passive filters, active filters serve to ampify the signal to provide better performance in terms of gain bandwidth and stability. Due to factors such as high input impedance and low output impedance, op amps achieve precise filter characteristics without the need for extra circuit components.

When selecting op amps for filtering applications, a specification such as high bandwidth allows for signal processing across a wide frequency range; low noise may also be desirable to maintain signal integrity within a system.

Temperature- and pressure-sensing applications typically involve the conversion of physical quantities to electrical signals that can be measured. In temperature-sensing, thermocouples may be used in designs, whereas pressure-sensitive applications make use of piezoelectric or capacitive sensors to capture analog data.

Op amps gain up signals read by these real-world sensors so they can be easily processed by following circuit components. Low input offset and drift enable accurate measurements over varying conditions and time. Depending on the application, low noise may be desired for signal integrity.

Op amps play a crucial role in preparing signals for analog-to-digital conversion by buffering and amplifying inputs to the ADC. In order to optimize readings out of the ADC, the data fed into it must be clean and readable. ADCs often require inputs to be within a specified range and of a certain voltage impedance; op amps provide this signal conditioning.

An amplifier is used to boost a signal to a readable level, and its low output impedance is used to drive an ADC. Impedance matching prevents loading effects at the input of the ADC, ensuring the signal is not distorted. ADCs often require a certain current to operate, and op amps have the ability to produce and maintain this output current drive to the ADC.