Op-Amp Output Behavior

The output terminal of the op-amp behaves like an ideal controlled voltage source from the fundamentals of electrical engineering. This means that the output voltage has a certain value that does not change with the output current. The output current is determined only by the load connected to the output.

The output voltage of the op-amp is calculated from the input voltage and the external circuit. There are two classic circuit configurations for which the output voltage can be calculated with the assumptions from the previous chapter.

The parameter “Output Voltage Swing” in the data sheet indicates the range in which the output voltage of the op-amp can lie. For the LM324, depending on the load, the output voltage only reaches about 1.5 V to 2 V below the positive supply voltage; towards the negative supply it gets closer. For simplicity, in this tutorial we calculate with an output range of ±10 V for a supply of ±12 V. If, for example, a voltage of 12 V is to be output, the op-amp outputs the maximum voltage of 10 V instead.

The following chapters look at basic amplifier circuits with which voltages can be amplified by defined factors.