LAB2REWRITE - ELCT 301 Laboratory Report#2 Experimental...

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ELCT 301 Laboratory Report #2 Experimental Design to Measure some Characteristics and Limitations of Op-Amps September 20, 2011 I hereby certify that I have complied with the Spirit and the Letter of the Carolinian Creed in preparing this report _________________________ Meredith Thomas Department of Electrical Engineering University of South Carolina Columbia, SC 29208
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Laboratory Grade: Pre-lab computation ____ of 10 Technical Content ____ of 60 Format/Presentation Clarity ____ of 20 Other ____ of 10 Late Deductions ____ ____ of 100 Student Comments: Grader Comments: Experimental Design to Measure some Characteristics and Limitations of Op-Amps I. Introduction When using an “Ideal” Op-Amp model, we assume that the circuit has infinite bandwidth. However, in real world operational amplifiers this is not the case. Real Op-Amps have limitations and specifications on the Gain-Bandwidth Product (GB) and Slew Rate (SR) which describe the actual performance of the Op-Amp. The objective of this lab is to understand the real-world functioning of the operational amplifier, and determine its Slew Rate and Gain- Bandwidth Product. After experimentally obtaining these measurements, simulations and specifications given in the data sheet will be used to analyze their accuracy. II. Theory The Slew Rate (SR) of an operational amplifier is the limit of how quickly the output voltage can adjust to a change of one of the inputs. An ideal op-amp is able to instantly and
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accurately output a signal which is a copy of the input, with some gain applied. Real-world op- amps, however, have limitations on the amount of time it takes to deliver large output signals operating at a high-frequency. At a lower frequency the output wave appears the same as the input. When the input voltage is increased and the frequency becomes higher, the output wave begins to change from the square pulse wave of the input to look like a trapezoid. This non-linear distortion effect occurs because the internal compensation capacitor of the op-amp has a limited current that can charge or discharge it. This in turn means the components of the op-amp cannot alter quickly enough to keep up with the input signal. By deriving the equation of an output signal, the Slew Rate can be found by Equation (1). SR = f p (2 π V r ) (1) The Slew Rate of an op-amp is specified in the datasheets of the amplifier by the manufacturer based its internal configuration. The operational amplifier used in this lab is a LM- 741 op-amp which has a 0.5 V/µs slew rate. The bigger the Slew Rate, the faster the op-amp. The faster the op-amp, the better it is able to accurately display changes in the signal without
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This note was uploaded on 10/25/2011 for the course ELCT 301 taught by Professor Santi during the Spring '09 term at South Carolina.

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LAB2REWRITE - ELCT 301 Laboratory Report#2 Experimental...

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