Applications of Operational Amplifier

Experiment 2

Applications of Operational Amplifier (Inverting amplifier, Non-Inverting amplifier and Adder)

Aim:

To design and construct an Inverting, Non-Inverting, and Adder circuits using 741 IC (Op-Amp) and obtain their output

Apparatus Required:

Theory:

An operational amplifier is a direct coupled high gain amplifier consisting of one or more differential amplifiers and usually followed by a level translator and an output stage which is usually a push-pull or push-pull complementary symmetry pair. An op- amp can be used to amplify ac as well as dc input signals and was originally designed for computing such mathematical functions as addition, subtraction, multiplication and integration. An Op-Amp can be configured in either the inverting or in the non-inverting mode.

Inverting Amplifier: As the name suggests the output of such amplifier is inverted as compared to the input signal. Such circuit is called Inverting Amplifier The inverted output signal means having a phase shift of 180’ as compared to the input signal. From the circuit Vo / Vin is ref. to as closed loop gain of the inverting op-amp. It is a ‘-‘ ve quantity because the closed – loOp-Amp reverses the sign of the i/p signal. Further it depends only on the ratio Rf / Ri and the closed loop gain stability is determined by the ratio. This circuit is also is called as sign “changer” with unity gain. If the ratio of Vo/Vin is K which is other than one the circuit is called “scale changer”.

Non – Inverting Amplifier: If the signal is applied to the non-inverting input terminal, the circuit amplifier without inverting the input signal. Such circuit is called Non – Inverting Amplifier. It is noted that it is also a ‘-‘ve feed –back system as o/p is being feed back to the inverting i/p terminal. The gain can be adjusted to unity or more, by proper selection of resistors R1 and Rf. Compared to the inverting amp, the i/p Resistance of the non-inverting amplifer is extremely large as the op-amp draws negligible current from the signal source.