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Unformatted text preview: Boise State University Department of Electrical and Computer Engineering ECE 212L Circuit Analysis and Design Lab Experiment #7: Basics of Operational Amplifiers 1 Objectives The objectives of this laboratory experiment are: To demonstrate the operation of a 741 op-amp by investigating common configurations such as the inverting amplifier, non-inverting amplifier, summing amplifier, and difference amplifier. 2 Theory An operational amplifier (op-amp for short) is a voltage amplifier with a very high voltage gain. An op-amp has two inputs: an inverting input, V n , and a non-inverting input, V p . When used in an open-loop configuration, the output voltage is governed by the relationship: V o = A ( V p V n ) (1) where A is the open-loop gain which is typically 10 4-10 5 . This gain varies widely from one op-amp to another and thus the op-amp is rarely used in an open-loop configuration. This gain can be reduced by using negative feedback. This involves connecting the output of the op-amp to the inverting input through a feedback network, usually composed of resistors. This will reduce the overall gain of the op-amp. A major advantage of this feedback loop is that the new gain can be controlled precisely and is practically independent of A which can vary from device to device. 6 7 8 1- + NC NC NC +V CC-V CC V n V V o p 5 2 3 4 Figure 1: LM741N Op-Amp (Top View) Figure 1 shows the pin configuration of 741 op-amp. This type of op-amp is an integrated circuit (IC) in a mini-DIP (Dual In-Line Package). The five relevant pins are shown in Figure 1....
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This document was uploaded on 11/01/2011 for the course ECE 212 at Boise State.
- Fall '08