1. Design an experiment to see how changing the open loop gain G of a noninverti
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Question
1. Design an experiment to see how changing the open loop gain G of a noninverting amplifier affects its bandwidth (the range of frequencies over which the gain remains constant) 2. Perform this experiment by simulation using the Orcad (Pspice & Capture) design tool Here is a suggested procedure to perform the simulation: a. Double click the OrCAD Capture icon on the desktop b. Go to File New Project. Type an appropriate name for your project+OK Keep the first choice selected->OK Create a blank project OK. c. Assemble the circuit shown in Fig. 6.6a. Use (VAC/SOURCE) for your input V3 d. From PSpice (top menu), select: New Simulation Profile. Name t for example: ac sweep. e. Set analysis type at: AC Sweep f. Use a frequency range of 1 Hz up to 10Meg Hz with 100 points /decade (Fig. 6.6b). g. Place a voltage marker on the output (pin 6) of the op amp. h. Print out the circuit diagram. i. Run your simulation to find the cuit frequency response i.e., how the voltage gain changes with changing the frequency of a sinusoidal input voltage). j. Print out the frequency response k. From the frequency response, find the bandwidth for that particular closed-loop gain. . Increase R to 20 k2 then repeat step i, j, and k. m. Increase R2 to 30 then repeat step and k. n. Increase R2 to 40 then repeat step i, j, and k. o. Tabulate the four values of G and their corresponding values of bandwidth. p. Wha t is your conclusion? Vs Figure 6.6
Explanation / Answer
While designing an opamp circuit oipamp gain bandwitdh is product is important.The opamp gain bandwidth product is generally for a particular type of opamp of open loop configuration and thye output is loaded:
gain bandwidth product =Av*f
where GB=opamp gain bandwidth product
I
Av=voltage gain
f=cut off frequency(Hz)
The opamp gain bandwidth product is constant for voltage feedback amplifiers bt it is not applicabe for current feedback amplifier because relationship between gain and bandwidth is not linear.
Therefore decreasing the gain by a factor of ten will increase the bandwidth by the same factor
In view incase of the very high gain operational amplifier it is possible to in effect ,exchange some of the open loop gain for bandwidth.For a circuit like this applying feedback will reduce the increases the bandwidth but reduce the gain
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