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MAE 3113 MEASUREMENTS AND INSTRUMENTATIONS SPRING 2006 Report due in Two weeks Lab 3b Operational Amplifiers (Week 2) FIRST: Finish any unfinished tasks from last week before you start. In this lab you will: 1. Design and test a Peak Detector: The peak detector is a circuit that "remembers" the peak value of a signal. When a positive voltage is fed to the non-inverting input after the capacitor has been momentarily shorted (reset), the output voltage of the op-amp forward biases the diode and charges up the capacitor. This charging last until the inverting and non-inverting inputs are at the same voltage, which is equal to the input voltage. When the non-inverting input voltage exceeds the voltage at the inverting input, which is also the voltage across the capacitor, the capacitor will charge up to the new peak value. Consequently, the capacitor voltage will always be equal to the greatest positive voltage applied to the non-inverting input. Once charged, the time that the peak detector "remembers" this peak value is typically several minutes and depends on the impedance of the load that is connected to the circuit. Consequently, the capacitor will slowly discharge towards zero. To minimize this rate of discharge, a voltage follower can be used to buffer the detector's output from any external load. Momentarily shorting the capacitor to ground will immediately set the output to zero.
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This note was uploaded on 09/14/2011 for the course MAE 3113 taught by Professor Staff during the Fall '11 term at Oklahoma State.

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