There are a bazillion (technical term) applications for op amps. The following section is an attempt to give you a basic understanding of just a few applications. None of the power supply connections are shown. Most op amp circuits used in audio use a ±15 volt power supply (especially when the audio equipment has a switching power supply). They can also be used with a single ended supply (no negative voltage) in head units and other such equipment that have no switching power supply.
The diagram below shows the schematic symbol for an op amp.
The positive input on the op amp is analogous to the green arrow. The height of the green arrow would be analogous to the voltage on the positive input. The sensor would be analogous to the valves which would also be analogous to the negative input of the op amp. The error correction would come at the output of the op amp (instead of the hydraulic actuator).
The next diagram has a resistor in series with the output of the op amp and the load which is to be driven by the op amp. The resistor represents anything that may be between the op amp and the load. The resistor could actually be a long run of wire, resistance in the copper of a printed circuit board or anything else that may cause the signal to be distorted. If the op amp didn't monitor the signal at the load, the signal would be distorted (in this case, the simple series resistance would only reduce the signal level). If the resistor would instead be an external circuit designed to increase the output current (such as the transistors, resistors, capacitors... of a power amplifier), the output of the op amp may not even resemble the final output signal. The op amp would do everything possible to get the final output to match the input signal.
DAHIANA A. ROSALES H.
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