Phys 351 lab 5

Phys 351 lab 5 - Lab 5: Op-Amps- Part 1 A: Open Loop...

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Lab 5: Op-Amps- Part 1 A: Open Loop Bandwidth and Phase Lag A-1. Open Loop Behavior In part A-1, an Op-Amp was wired up to a potentiometer as shown in the figure below. - The output voltage when V3>0 was observed to be 14.7V. - The output voltage when V3<0 was observed to be -14.0V. - The output voltage as V3 approaches zero should be Zero. This is because there is no voltage to be amplified, and A*V3= 0 when V3 = 0. It was observed that this point was very hard to reach, and it would jump from -14V to 14.7V but never stabilize on zero. - Swapping the input from V3 to V2 led to the following results, when V2>0 it was observed that the output was -14.1V. When V2<0, the output was observed to be 14.7V. Changing the input from the positive terminal to the negative terminal led to an inverted output. Section B: Inverting and Non-Inverting Op-Amps B-1. Inverting Amplifier In part B-1, an inverting amplifier was built such that the output amplitude was 14Vpp. A sinusoidal 1kHz signal was applied to the input. The following circuit was built
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- With an input voltage of 1.5V, an output voltage of 14.0 was observed. These two measurements give a gain of -9.33. The expected gain would be -10 Ohm / 1 Ohm, or a gain of -10. The percent difference is 6.7%. - The frequency was scanned from a range of 100Hz to 20MHz and the output voltages measured at each frequency. The following figure shows the data in graphical form. Gain vs Frequency 0 1 2 3 4 5 6 7 8 9 10 3.5 8.5 13.5 ln(Frequency) Gain Series1 - The same procedure was done on EWB and the following bode plot was produced - The f3db point found in lab was observed to be around 100kHz. The phase difference at this point was observed to be 200 degrees. -
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This note was uploaded on 11/03/2009 for the course PHYS 351 taught by Professor Staff during the Spring '08 term at UNC.

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Phys 351 lab 5 - Lab 5: Op-Amps- Part 1 A: Open Loop...

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