1.5 OPERATIONAL AMPLIFIERS

An operational amplifier (op-amp) is a high-gain direct-coupled amplifier and, as shown in Fig. 1.41, has three basic building blocks—a differential amplifier as an input stage, dc-level shifter or level translator and an output power stage.

The differential amplifier gives an output proportional to the difference between the two inputs. As the op-amp is a direct-coupled amplifier, the output is referenced to a dc voltage. If there is a need to ensure that the output is referenced to the zero level, there arises the need for a level translator or a dc level shifter, which translates the dc voltage at the output to zero. An operational amplifier, unless otherwise warranted, needs to be balanced before it is used for ...

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