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# Ideal Op Amps - PowerPoint PPT Presentation

Ideal Op Amps. Z in =  Implies zero input current Z out = 0 (without feedback) Implies a perfect voltage source Differential voltage gain G diff =  (without feedback) Common-mode voltage gain G CM = 0 Above two features imply a perfect differential amplifier

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## PowerPoint Slideshow about ' Ideal Op Amps' - phelan-olson

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• Zin = 

• Implies zero input current

• Zout = 0 (without feedback)

• Implies a perfect voltage source

• Differential voltage gain Gdiff = (without feedback)

• Common-mode voltage gain GCM = 0

• Above two features imply a perfect differential amplifier

• Vout = 0 when both inputs are at the same voltage (zero “offset voltage”)

• Implies perfect transistor matching at the inputs

• Output can change instantaneously (infinite “slew rate”)

• The output attempts to do whatever is necessary to make the voltage difference between the two inputs zero (consequence of very high voltage gain).

 But asymmetries between the input terminals cause output error signals!

• The inputs draw “no” current (consequence of very high input impedance).

 In reality, the inputs draw some current!

(Introductory Electronics, Simpson, 2nd Ed.)

(Introductory Electronics, Simpson, 2nd Ed.)

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

(Iio = Ios)

(Introductory Electronics, Simpson, 2nd Ed.)

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

(Vio = Vos)

(Introductory Electronics, Simpson, 2nd Ed.)

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

Measuring IB, Ios, Vos

(Lab 9–1)

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

• The circuits below will always give a saturated output after a short time. Why?

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

(Lab 9–1)

(Introductory Electronics, Simpson, 2nd Ed.)

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

(Lab 9–2)

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

(Lab 9–3)

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

(Lab 9–5)

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

(Lab 9–5)

output glitch

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

(Lab 9–6)

R2

D1

R1

D2

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

(Lab 9–7)

VC

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

(Lab 9–7)

VC =10 V

(Student Manual for The Art of Electronics, Hayes and Horowitz, 2nd Ed.)

(The Art of Electronics, Horowitz and Hill, 2nd Ed.)

vin (capacitively coupled)

Ri

R2

R1

C

(The Art of Electronics, Horowitz and Hill, 2nd Ed.)

(The Art of Electronics, Horowitz and Hill, 2nd Ed.)