E E 2315 Lecture 08 - Introduction to Operational Amplifiers

Operational Amplifiers Ideal operational amplifiers are easily analyzed Assumptions for ideal operation are realistic Inexpensive commercial Op-Amps available as integrated circuits Practical applications for instrumentation, signal processing and control circuits

 A741 Pinout

Op Amp Terminals

Op Amp Terminal Currents

Op Amp Terminal Voltages

Equivalent Circuit

Assumptions for Ideal Op Amp Open loop Gain, A    v p - v n  0 Then v p - v n  0  R i   R i    i p  0 and i n  0 Gain is linear up to the saturation voltage Saturation voltage equals power supply voltage

Open-Loop Characteristics

Inverting Amplifier and V n = 0 and i n = 0. Then KCL at node n yields:

Saturated Mode Inverting Amplifier with +V cc = 5 V and V cc = -5V. R f = 10 k  and R g = 1 k 

Non-Inverting Amplifier KCL at node n: v n = v p = v g

Summing Amplifier (1/2)

Summing Amplifier (2/2)

Difference Amplifier (1/3) n:

Difference Amplifier (2/3) Voltage p:

Difference Amplifier (3/3) Substitute: into: and simplify: If: Then:

Analyzing an OpAmp Circuit