![Non-inverting Amplifier
Vin Vout
Rin
Rf
Iin
If
Vin
+
Due to virtual ground:
VINV = VNI = Vin
If = (Vout–Vin) / Rf = Iin= Vin / Rin
Vout = [1+ (Rf / Rin )] Vin](https://image.slidesharecdn.com/operationalamp-230815095309-4acb3f82/85/OPERATIONAL-AMP-ppt-20-320.jpg)
![Inverting Adder
V2
V3
V1
R3
R2
R1
Rf
+
Vout
Vout= Rf [(V1 / R1)+ (V2 / R2)+ (V3 / R3)]](https://image.slidesharecdn.com/operationalamp-230815095309-4acb3f82/85/OPERATIONAL-AMP-ppt-22-320.jpg)
![Subtractor Analysis
Vout = – V1Rf / Rin + [1+ (Rf / Rin )] V’
= Rf (V2 – V1) / Rin
V2
V1
Rf
Rin
Rf
Rin
Vout
V’
V’ = V2Rf / (Rf+Rin)
V2](https://image.slidesharecdn.com/operationalamp-230815095309-4acb3f82/85/OPERATIONAL-AMP-ppt-24-320.jpg)
OPERATIONAL AMP.ppt
- 2. Typical Op Amp IC Packages Dual-in-Line package (DIP) Metal Can Package
- 3. Op Amp Pin-out connections Dual-in-Line Plastic Package OFFSET NULL OFFSET NULL
- 4. Op Amp Pin-outs Metal Can
- 5. WHAT IS INSIDE AN OP AMP?
- 6. Phases of output signal wrt input input
- 8. Two matched transistors form a differential amplifier input 0 V -VEE+0.7 V Constant current = I1+I2 I1 I2 VC1=VCC-I1R2 VC2=VCC-I2R4
- 9. Transisterized Differential Amplifier Double ended input - double ended output diff. amp: vout=A (v1-v2) v1 v2 vout - +
- 11. ● Single ended output Non- inverting input Inverting input Single Ended Differential Amplifier (commonly used in op-amps)
- 12. Op Amp stages with pin-outs of IC741 2 4 7 6 3
- 13. Op amp Comparator • Open loop gain of op amp is defined as: AOL = Vo / VD where VD = VNI – VINV • Open loop gain of op amp is very high (ideally infinite). • Any small difference between VNI and VINV results into saturation of output voltage ±VSAT i.e. for VNI < VINV output is – VSAT and for VNI > VINV output is + VSAT • Value of VSAT is limited by the supply voltage of op amp
- 14. Op amp Voltage Level Detector VOUT + - VREF VIN = +VSAT for VIN>VREF = -VSAT for VIN<VREF
- 15. Important features of Op Amp 1. High open loop gain (ideally infinite) which implies that even the smallest difference between the two inputs results into saturated output voltage 2. High input impedance (ideally infinite) implies that there is no current flowing into the input of an op amp
- 16. Virtual Ground These two conditions give rise to VIRTUAL GROUND, where the voltages at both the inputs are maintained at exactly same level. To achieve this condition, a feedback circuit between the output and the inverting input terminal of the op amp is necessary. This results into many applications of op amp, which qualify it to be OPERATIONAL: adder, subtractor, multiplier, divider etc.
- 18. Inverting Amplifier Multiplier/Divider circuit, whose gain is decided by the values of resistors Rf Rin Vin Vout +
- 19. Inverting Amplifier Analysis Iin Rf Rin Vin Vout If + Due to virtual ground: Iin= Vin / Rin= If = – ( Vout / Rf ) Vout= – (Rf / Rin ) Vin Rf > Rin →multiplier Rf < Rin→ divider
- 20. Non-inverting Amplifier Vin Vout Rin Rf Iin If Vin + Due to virtual ground: VINV = VNI = Vin If = (Vout–Vin) / Rf = Iin= Vin / Rin Vout = [1+ (Rf / Rin )] Vin
- 21. Unity Gain Amplifier (Non-inverting Buffer) + – Vin Vout=Vin
- 22. Inverting Adder V2 V3 V1 R3 R2 R1 Rf + Vout Vout= Rf [(V1 / R1)+ (V2 / R2)+ (V3 / R3)]
- 24. Subtractor Analysis Vout = – V1Rf / Rin + [1+ (Rf / Rin )] V’ = Rf (V2 – V1) / Rin V2 V1 Rf Rin Rf Rin Vout V’ V’ = V2Rf / (Rf+Rin) V2
- 25. Op amp integrator Vin Vout Rin Cf Vout= – (1 / Rin Cf ) ∫ Vin dt Iin If Iin= Vin / Ri n= If = – Cf ( dVout / dt )
- 26. Op amp Differentiator Vin Vout Cin Rf Vout= – Rf Cin (dVin / dt ) If Iin Iin= CindVin /dt = If = – Vout / Rf
- 28. Common Mode Rejection Ratio (CMRR) • It is the ability of an op amp to reject the signal which is present at its both inputs simultaneously i.e. the common mode signal • CMRR = AOL / ACM, where ACM is common mode voltage gain defined by Vout / VCM • Ideally CMRR is infinite • For IC 741 it is 90 dB
- 29. Slew Rate • Maximum rate of change of output voltage (when typically a step voltage is given at the input terminal) Step Input Vout t dVout / dt
- 30. Slew Rate (cont…) • Slew rate is caused by the finite response time of the circuit elements of an op amp • It limits the highest possible frequency of operation Vin Vout Expected Voltage t
- 31. Open Loop Gain • AOL is ideally infinite • In case of typical practical op amp like IC 741 it is of the order of 105 i.e. about 100 dB Input Resistance • RI is ideally infinite • In case of IC 741 it is 2 MΩ Output Resistance • RO is ideally zero • In case of IC 741 it is 75 Ω
- 32. Input Offset Voltage • Small voltage needed to be applied between INV and NI terminals to get zero output voltage • Ideally it should be 0 V (CM operation) Output Offset Voltage • Under common mode operation, output voltage should be zero, but due to mismatch is devices it is non-zero (Can be corrected by applying voltage between Pins 1 and 5 of IC 741)
- 33. Summary • Op amp can be used for various (mathematical) operations like addition, subtraction, multiplication, division, differentiation, integration etc. • Infinite open loop gain and infinite input resistance give rise to VIRTUAL GROUND • Op amp is available in a simple to use IC form which require dual supply • Many other applications can be implemented using op amp
- 34. ACKNOWLEDGMENT Some circuits in this presentation are based on following materials: • HANDBOOK OF OPERATIONAL AMPLIFIER APPLICATIONS by Texas Instruments • www.williamson-labs.com
- 35. Thank you !