# prob 4 - Joe Doyle Take Home Design Simulation(Prob#4 My...

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Joe Doyle Take Home Design Simulation (Prob. #4) My task in this design problem is to use the natural log op amp in combination with other op amps in order to produce the voltage output ln(Vi). The output voltage of the natural log op amp is Vo=- nVtln(Vi)+nVtln(R1+Is). The following assumptions will be used: nVt=47.6mV, Is=3.035nA, R1=1k-ohm, and available power supplies are +/-15VDC. A requirement in this design is to use a maximum of three uA741 op amps because PSpice will not run if the design exceeds 64 nodes, which I found out first hand. I tried several designs with three op amps but none of them worked for me. I resorted to using four op amps because it is the only way I found to produce the required output voltage. I will be unable to run the simulation for this assignment but I will do my best to prove that the output voltage will be ln(Vi). In general my design includes the natural log op amp, followed by the differentiator, followed by the integrator, and then an inverting op amp. Here is the math I used in my design process:

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I attempted to run this circuit in PSpice but it was too large. The following page includes my
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## This document was uploaded on 12/03/2009.

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prob 4 - Joe Doyle Take Home Design Simulation(Prob#4 My...

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