Chap.4-handout

# Chap.4-handout - 4 Read sections 4.1 thru 4.5 section 4.6...

This preview shows pages 1–8. Sign up to view the full content.

9/28/2010 1 Diodes 1 Read sections 4.1 thru 4.5 section 4.6 skipped section 4.7 skipped Chapter Expectation: know Diode I-V Characteristics : Forward, Reverse, and reverse Breakdown know various Diode Models and apply them to circuit analysis Know to analyze and design simple diode circuits: rectifier, regulator, filtered rectifier, .. 1 4 Various Semiconductor Products 2

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
9/28/2010 2 Diode I-V Characteristics 3 Diode I-V Summary 4
9/28/2010 3 1. Ideal Diodes Circuit Symbol: forward reverse ( short circuit) I-V Characteristics: open short V < 0 V > 0 I-V : Model: Application Example: 5 6 Application: (1) rectifier using ideal diode For V D > 0 (forward) input waveform output waveform For V D < 0 (reverse)

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
9/28/2010 4 Ex.3.3) V P =10V R=1 k W Peak diode current 7 = 3.2V 3.2V 10 V Application: (1) rectifier - Ex.3.3 DC component of v O q =0 q = p q =2 p 2. Diode I-V Characteristics (terminal char.) -- REAL DIODE ) 1 ( / T nV v s e I i i n =ideality factor=between 1 and 2 V T =thermal voltage=kT/q I S =saturation current parameter Forward and Reverse, but not Breakdown 8
9/28/2010 5 2. Diode I-V Characteristics (terminal char.) -- REAL DIODE Forward Expand x-axis i 2.1 Forward Bias Region i ≈ 0 for v < 0.5V 0.5 V = Cut-in voltage Diode is fully on at v = 0.7 V = Turn-On voltage Cut-in voltage Turn-On voltage 9 2. Diode I-V Characteristics (terminal char.) -- REAL DIODE Expand y-axis i 2.2 Reverse-Bias Region : v < 0V I = I s [exp(v/nV T ) – 1] ≈ - I s I S = Reverse Saturation Current ~ typically 10 pA/cm 2 Real device: reverse current >> I S I S 10

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
9/28/2010 6 2.1 Forward Bias Region ) 1 ( / T nV v s e I i Where, V T = kT/q =25 mV at T=300K, k=Boltzmann const.=1.38x10 -23 joules/K, and n = ideality factor = between 1 and 2 1= most ideal, IC device; 2= least ideal, many traps, discrete device Ex) For nearly all forward bias regions, i >> I s i = I S exp(v/nV T ) [ i vs. v ] v = nV T ln(i/I s ) = 2.3 nV T log(i/I s ) [ v vs. i ] Ex) Q: you measured the diode voltages at two different current values how are they related? Ans: v 2 -v 1 = 2.3 nV T log(i 2 /I s ) - 2.3 nV T log(i 1 /I s ) = 2.3 nV T log(i 2 /i 1 ) Ex.3.6) For a silicon diode with n=1.5, find the change in voltage for a current change from 0.1 mA to 10 mA Answer) i 2 /i 1 = 10 mA/0.1 mA = 100 v 2 -v 1 = 2.3 n V T log(100) = 2.3*1.5*25 mV*2 = 172.5mV v 2 -v 1 = 2.3 nV T log(i 2 /i 1 ) 11 Modeling the Forward Characteristics 12
9/28/2010 7 3. Forward Characteristics Diode Models Piecewise Linear Model Const. Voltage Drop Model Small-signal model 13 i D = I s exp(v D /nV T ) Exponential Model Ideal Diode Model Const.Volt.Drop Model SmallSignal Model Piecewise Linear Model ac circuits 14 3. Forward Characteristics : Summary -- five Diode Models

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern