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    Simple OP amp circuits with feedback

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    Hi John

    could you help me out with these? see attachment

    © BrainMass Inc. brainmass.com October 10, 2019, 8:28 am ad1c9bdddf
    https://brainmass.com/engineering/electronic-engineering/simple-amp-circuits-feedback-628177

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    Op-amp circuits Questions & Solutions
    3.

    (a)
    The output function V_out=8V_4+4V_3+2V_2+V_1 can be realised by the following Opamp circuit (an explanation below)

    Circuit operation:
    Consider input V_4 when switched to high input rail current i_4=V/R flows
    Consider input V_3 when switched to high input rail current i_3=V/(R/2)=2 V/R flows
    Consider input V_3 when switched to high input rail current i_2=V/(R/4)=4 V/R flows
    Consider input V_3 when switched to high input rail current i_1=V/(R/8)=8 V/R flows
    Total current is thus the sum of the branch currents so we can write

    i=i_1+i_2+i_3+i_4=8 V/R+4 V/R+2 V/R+V/R

    The feedback resistor provides negative feedback so the output voltage is given by Ohm's law as

    V_O=-iR_F=-8 R_F/R V-4 R_F/R V-2 R_F/R V-R_F/R V

    Finally add a second stage negative feedback Opamp circuit with unity gain given by ...

    Solution Summary

    2 Questions and solutions involving simple OP amp circuits with feedback, one question concerns a 4 bit DAC utilising an opamp circuit, the other question analysis of potentiometer negative feedback op-amp circuit

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