IN DETAIL operational amplifier.pptx

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1. HARISHCHANDRA POST GRADUATE COLLEGE , VARANASI OPERATIONAL AMPLIFIER ANKIT GUPTA MSc. PHYSICS ( -SEM)  

2. A M P L I F I E R It is an electronic circuit or device which increases the amplitude of a signal

3. O P E R A T I O NA L A M P L I F I E R ( O P A M P ) Historically an Op Amp was designed to perform such mathematical operations as addition, subtraction, integration and differentiation. Hence t h e n a m e O p e r ati on al A mp lifi er . Background Originally invented in early 1940s using vacuum tube technology – Initial purpose was to execute math operations in analog electronic calculating machines Shrunk in size with invention of transistor Most now made on integrated circuit (IC) Huge variety of applications, low cost, and ease of mass production make them extremely popular

4. I CS

5. 7 4 1 O p - A m p – In t e r n a l C i r c u i t r y

6. O P A MP – A MULTISTAGE A MPLIFIER Di f f e r e n tial A m p lifier s ta g e High gain CE amplifier stage Class B push pull emitter follower Differential Amplifier More stages of gain Class B Push pull Amplifier

7. O p A mp E qu i v ale n t C irc u it

8. I d e a l O p A m p Z in = ∞ Z out = A V = ∞ P r a c t i c a l O p A m p   Z in Z out = 2M Ω = 100 Ω A V = 10 5 V o l t a g e T r an s f e r C h a r a c te r i s t ic

9. A PP L I C A T I O N S N o n -I nv e rt i n g A m p l i fier

10. Inv e rt i ng Am pl i fier

11. O p - Am p S um m ing Amp l ifi e r O p - Am p Di f f e r e n tial A m p lifier If R 1 = R 2 and R f = R g :

12. Op-Amp Integrator V o = - Op-Amp Differentiator

13. Low-pass Filter (active) Cutoff frequency This works because the capacitor needs time to charge . High pass filter (active)

14. Applications of Op-Amps Elect ro c ar d i o g r am (E K G) A m p lificati o n Need to measure difference in voltage from lead 1 and lead 2 60 Hz interference from electrical equipment

15. Simple EKG circuit Uses differential amplifier to cancel common mode signal and amplify differential mode signal Realistic EKG circuit Uses two non-inverting amplifiers to first amplify voltage from each lead, followed by differential amplifier Forms an “instrumentation amplifier”

16. Strain Gauge Use a Wheatstone bridge to determine the strain of an element by measuring the change in resistance of a strain gauge (No strain) Balanced Bridge R # 1 = R # 2 (Strain) Unbalanced Bridge R # 1 ≠ R #2

17. Half-Bridge Arrangement Using KCL at the inverting and non-inverting terminals of the op amp we find that  ε ~ V o = 2 Δ R ( R f /R 2 ) R + Δ R R f - + V + V cc - + - V cc R f V ref + R R - Δ R R Op amp used to amplify output from strain gauge

18. O p Amp s Applic a t i ons Audio amplifiers Speakers and microphone circuits in cell phones, computers, mpg players, boom boxes, etc. Instrumentation amplifiers Biomedical systems including heart monitors and oxygen sensors. Power amplifiers Analog computers Combination of integrators, differentiators, summing amplifiers, and multipliers