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# lesson17 - Lesson 17 Op-Amps #2 (Section 4-4) (CLO 4-2)...

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Lesson 17 – Op-Amps #2 (Section 4-4) (CLO 4-2) This is the second lesson on Op-Amps. The goal is to get through developing the four basic building blocks: Inverter, Non-inverter (and Follower), Summer, and Subtractor. It is important that the students learn how to analyze Op-Amp circuits using Node Analysis. Last class we developed the non-inverting Op-Amp. Quickly review that analysis including the two key Op-Amp equations, and talk about the Follower. In discussing the Follower, start with the non- inverter drawn on the board and ask them to design a unity gain amplifier. They quickly realize that R 2 must be equal to zero. Once R 2 is gone R 1 can be anything – so why not an Open circuit? Ask them what K is for this circuit. It equals 1, of course. How is that any different from a piece of wire? On the surface, it appears that there is no difference. Suppose you wanted to measure the voltage across a 10 M resistor using a standard DMM with a 10 M internal resistance. The DMM would not measure the correct voltage because the DMM’s internal resistance is in parallel with the resistor you are trying to measure the voltage across. The DMM would “load” the circuit. The meter provides a path for current other than through the load. In this case, the connection to the DMM was made through a wire with a K of 1. However, if we were to insert a Follower between the load and the DMM we would no longer

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## This note was uploaded on 10/12/2010 for the course MAE 140 taught by Professor Mauriciodeoliveria during the Spring '08 term at UCSD.

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lesson17 - Lesson 17 Op-Amps #2 (Section 4-4) (CLO 4-2)...

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