Mathematica+hw+2+

# Mathematica+hw+2+ - equations to find V th and R th and...

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EECS 70B Spring 2011 Due on Friday. week 4 Mathematica Homework 2 1. Diode turn on voltage: Use Mathematica to plot the forward active (V D >0) I-V characteristics ( / ( ) (e 1) D T V V D s I V I = - ) of an ideal diode, (I s =10 -15 A, V T =0.026V) in which the current is expressed in A, mA, μ A and nA scales. Plot your I-V characteristics from 0 volt until the diode is ‘turned’ on. Hint: use PlotRange to limit the current level in your plot. 2. Thevenin Equivalent Circuit for Op Amp Inverting Amplifier: An Op Amp inverting amplifier is shown below along with the Op Amp model: O U T 1 + 3 - 2 V + 4 V - 1 1 R 1 1 k R 2 2 k R L 1 k 0 Vo Vs R i 1 M A vd R o 5 0 0 _ + vd (A=10^6) Vo Once you insert the Op Amp model, the inverting amplifier circuit looks like this: R i 1 1 M A vi R o 1 5 0 0 + vi (A=10^6) _ V s 0 R 2 2 k R 1 1 k R L 1 k Vo + _ The boxed portion of the circuit can be represented using Thevenin equivalent circuit. Find V th and R th of this boxed portion. Calculate R th using both methods (R th =V oc /I sc or R th =R i looking into the source port with Vs removed). You should first formulate the

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Unformatted text preview: equations to find V th and R th and then use Mathematica to find their numerical values. _ + Hint: Use Solve function. You should get a very small Rth. This explains why Vo for Op Amp inverting amplifiers are insensitive to RL because the voltage divider effect is negligible. 3. Exact Solution for Diode Resistor Circuit : (1) Consider a diode and R (10kW) connected in series with a DC voltage source (Vs=5V). Use Mathematica to calculate I D and V D by solving the exact transcendental equation using the diode equation, / ( ) (e 1) D T V V D s I V I =-where I s =10-15 A, V T =0.026V. Hint: Use FindRoot function. (2) If we vary Vs from 0 to 5V use Mathematica to calculate the values for V D by solving the exact transcendental equation. Plot your calculated V D versus Vs. Also plot the corresponding Vd vs. Vs based on the hand calculation using the ON-OFF model....
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## This note was uploaded on 02/06/2012 for the course EECS 70B taught by Professor Henrylee during the Spring '08 term at UC Irvine.

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Mathematica+hw+2+ - equations to find V th and R th and...

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