Lecture3a

# Lecture3a - D , i D- ? We could get V 1 and the slope from...

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Lecture 3. ANALYSIS OF DIODE CIRCUITS Objectives: Perform analysis of nonlinear circuits graphically Obtain piecewise linear models Perform analysis of nonlinear circuits analytically Topics: The graphical solution method Piecewise linear approximation Examples

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Circuits Analysis Find load voltage and current: Conventional method:
Graphical Method We could still obtain a Thevenin circuit, but we have a nonlinear device (diode) Solution – the intersection point What if we change V or any of the resistors? What if we flip the diode?

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Piecewise Linear Approximation - could be used for analytical solution when we have nonlinear elements y(x) – complex function (could be nonlinear, high-order) Linear approximation: APPLIED TO DIODES: - same diode as in the previous example A – operating point Good only in the vicinity of A, not good around B
EXAMPLE Same diode as before (I s =10 -11 A, η =1.6, V T =0.025), operating point around I D =1mA Piecewise linear model - ? Exact v

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Unformatted text preview: D , i D- ? We could get V 1 and the slope from V-I curve or we can use diode V-I equation We know i D =I D =1mA, find v D from V-I eq. EXAMPLE (continued) Piecewise Linear Model of the Zener Diode- same approach with V f and r D for the forward bias condition Application of Piecewise Linear Models- why not just the graphical solution method? Piecewise linear approximation is a powerful approach when you have ac sources in the circuit EXAMPLE Circuit with a square-law device (A=1mA/V 2 , V TR =0V) Problem: we do not have a single solution point, since v TH const v TH_MIN = v TH_MAX = v TH_MED = EXAMPLE (continued) a) We could use the device V-I equation to solve for v S and i S : From circuit From device V-I equation: Combine both: b) Use piecewise linear model From the approximation circuit: for v TH =3.8V (point A): for v TH =2.2V (point B):...
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## Lecture3a - D , i D- ? We could get V 1 and the slope from...

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