741 op amp circuit n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
741 Op-Amp Circuit PowerPoint Presentation
Download Presentation
741 Op-Amp Circuit

Loading in 2 Seconds...

play fullscreen
1 / 22

741 Op-Amp Circuit - PowerPoint PPT Presentation


  • 473 Views
  • Uploaded on

741 Op-Amp Circuit . Section 8.1 ( Razavi ) Chapter 12 ( Sedra Smith). History. The first uA741 Op-Amp was designed by Bob Widlar in 1963 at Fairchild Semidconductor . uA702 sold for 300 a piece. uA709 was sold for 70 a piece.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about '741 Op-Amp Circuit' - rosina


Download Now An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
741 op amp circuit

741 Op-Amp Circuit

Section 8.1 (Razavi)

Chapter 12 (Sedra Smith)

history
History
  • The first uA741 Op-Amp was designed by Bob Widlar in 1963 at Fairchild Semidconductor.
    • uA702 sold for 300 a piece.
    • uA709 was sold for 70 a piece.
  • Bob asked for a raise, didn’t get it, so he quit. Bob sent to National Semiconductor.
    • LM101

http://en.wikipedia.org/wiki/Bob_Widlar

history1
History
  • David Fullagar (Fairchild)
    • Scrutinize LM 101
    • Incorporated a 30 pF Cap.
    • uA741 was introduced.
    • Gordon Moore
bjt op amp1
BJT Op-Amp

Input-Stage

Bias

Reference

Bias

Current

Second-Stage

Input-Stage

Output-Stage

reference bias current
Reference Bias Current

VCC=15 V

VEE=-15 V

VBE11=0.7 V

VEB12=0.7 V

IREF=0.73 mA

input stage bias
Input-Stage Bias

IREF=0.73 mA

R4=5 KΩ

(IS10=IS11, assumption)

Solve through trial and error

IC10=19 uA

input stage 1
Input Stage (1)

From previous

Calculation:

IC10=19 uA

(from symmetry)

(β is high )

(~0)

negative feedback
Negative Feedback

(2)

(3)

(1)

(4)

(constant)

input stage 3
Input Stage (3)

(IB1)

(IB2)

(Input Bias Current)

(Input Offset Current)

input resistance
Input Resistance

(AC Ground)

R into the emitter of Q3: 1/gm3

R into the base of Q1: rπ1+β1/gm3

Differential resistance 2(rπ1+β1/gm3)

gm=IC/VT

Large input resistance since IC is kept small!

Typical input impedance is in excess of 2 MOhms

second stage bias
Second-Stage Bias

0.75IS12=IS13B

IC12=0.73 mA

IC13B=0.55 mA

IC17=IC13B

(0)

output stage bias
Output Stage Bias

(0)

IS13,A=0.25IS12

IC23=0.25IREF

Assume

VBE18=VBE19=0.6 V

Βp=50

Βn=200

ICE23=180 uA

IR10=15 uA

IE18=IE23-IR10

IB18=IC18/200=0.8 uA

IE19=IB18+IR10

VBB=VBE18+VBE19

(Output resistance is small)

(0)

equivalent circuit of an op amp
Equivalent Circuit of an Op-Amp

Characteristics:

Negligible input current

Large input AC resistance

Small AC output resistanceLarge Voltage Gain

op amp as an amplifier
Op-Amp as an Amplifier

(non-inverting input)

(inverting input)

Op-Amp is a circuit that amplifies the difference

between the inputs.

consequence of large gain
Consequence of Large Gain

As Ao approaches infinity, Vin1-Vin2 approaches 0.

unity gain buffer
Unity Gain Buffer

(If A0 is 1000, Vout/Vin=0.999)