Chapter 10: Khuếch đại thuật toán pptx

 Characters of circuits depend on outside circuit structure, not the opamp itself  Gain AV: very high, ideally ∞  Zin: very large, ideally ∞  Zout: very small, ideally 0  Current e

Symbol

Example

 Characters of circuits depend on outside circuit structure, not the opamp itself

 Gain AV: very high, ideally ∞

 Zin: very large, ideally ∞

 Zout: very small, ideally 0

 Current entering the amp at either terminal: extremely small, ideally 0

 Voltage out (when voltages into each other are equal): small, ideally 0

 Bandwidth: broad, ideally infinite

 Input: 2 inputs (positive and negative)

ground

source apply between 2 inputs

 Output: 1 or 2 outputs, typically 1 output

 Mode gain:

 Differential-mode gain Adm - large

about 103-105

 Input impedance: large

 Output impedance: small

 Input: symmetric

 Addition and subtraction circuits

 Integration and differential circuits

 Multi-stages circuit

 Advance applications

 Current-controlled voltage source

 Voltage-controlled current source

Non-inverting fixed-gain amplifier

Non-inverting fixed-gain amplifier

A = 1+Rf/R1=101Vo=101Vi

Inverting fixed-gain amplifier

Voltage addition

Vo = -V1Rf/R1-V2Rf/R2 –V3Rf/R3

If V1=V2=V3 then:

A= -Rf/R1-Rf/R2 –Rf/R3

Voltage subtraction

Vout1 = -Rf/R1V1

Vout = -Rf/R2V2 - Rf/R2Vout1 = -Rf/R2V2 + Rf/R2V1

= -Rf/R2(V1 – V2)

Voltage subtraction with 1 amp

Uni-gain (buffer) amplifier

 Provide required input and output resistant stage

 Provide multiple identical output signals

Voltage-controlled voltage source

 Vo=(-Rf/R1)V1

 Vo=(1+Rf/R1)V1

Voltage-controlled current source

 Io=V1/R1

Current-controlled voltage source

 Vo=-I1RL

Current-controlled current source

 Io=I1(R2+R1)/R2

Integration circuit

 Vo=(Vi/RC)0ƒTVi(t)dt+Vout(t=0)

Differential circuit

 Vo=-RC dVi/dt

 Low pass filter

 High pass filter

 Band pass filter

1 st order low pass filter

 Cutoff frequency: fOH=1/(2πR1C1)

 Voltage gain below cutoff freq: Av=1+Rf/RG

2 nd order low pass filter

 Cutoff frequency: fOH=1/(2πR1C1)

 Voltage gain below cutoff freq: Av=1+Rf/RG

1 st and 2 nd order high pass filter

 Cutoff frequency: fOL=1/(2πR1C1)

 Voltage gain above cutoff freq: Av=1+Rf/RG

Band pass filter

Multi-stages gain

A = A1*A2*A3

741 application-Light activated alerter

12V battery monitor

 Chapter 14: 1, 4, 9, 10, 12, 15, 17, 18

 Chapter 15: 1, 6, 8, 11, 14, 16, 17

OpAmp 741

 Maximum ratings

 Inside structure

Maximum ratings

OpAmp 741 inside structure

Q12

R10 40k

Q5

R8 100

Cc 30p

Q1

R3 50k

R7 27k

Vin+

Q15

R1 1k

Vin-R4 5k Q11

Biasing Current Sources

 Generates reference bias current through R5

 The opAmp reference current is:

Iref=[VCC-VEB12-VBE11-(-VEE)]/R5

 For VCC=VEE=15V and

VBE11=VBE12=0.7V, we have IREF=0.73mA

Q10

Q9 Q12

R5

39k

R4 5k Q11

Q8

R3

50 k

R2 1k Q2

Input Stage:

DC Analysis -2

 From symmetry we see that

IC1=IC2=I, and if the npn β is large, then IE3=IE4=I

 Analysis continues:

Input Stage:

DC Analysis -3

 Analysis of the active load:

Second (Intermediate) Stage

 Transistor Q16 acts as an emitter-follower giving this stage a high input resistance

 Capacitor Cc provides frequency

compensation using the Miller compensation technique

Output Stage

 Provides the opAmp with a low output resistance

 Class AB output stage provides

fairly high current load capabilities without hindering power dissipation in the IC

R7 27k

R6 27k

Q20 R10

40 k

Output Stage:

DC Analysis

 Q13a delivers a current of 0.25IREF, so we can say: IC23=IE23=0.25IREF=180µA

 Assuming VBE18 = 0.6V, then IR10=15µA, IE18=180-15=165µA and IC18=IE18=165µA

 IC19=IE19=IB18+IR10=15.8µA

Short Circuit Protection

 These transistors are normally off

 They only conduct in the event that a large current is drawn from the output terminal (i.e a short circuit)

R11 50k Q24

Q22