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SJTU Zhou Lingling1 Chapter 7 Operational-Amplifier and its Applications.

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Presentation on theme: "SJTU Zhou Lingling1 Chapter 7 Operational-Amplifier and its Applications."— Presentation transcript:

1 SJTU Zhou Lingling1 Chapter 7 Operational-Amplifier and its Applications

2 SJTU Zhou Lingling2 Outline Introduction The 741 Op-Amp Circuit The ideal Op Amp The inverting configuration The noninverting configuration Integrator and differentiator The antoniou Inductance-simulation Circuit The Op Amp-RC Resonator Bistable Circuit Application of the bistable circuit as a comparator

3 SJTU Zhou Lingling3 Introduction Analog ICs include operational amplifiers, analog multipliers, A/D converters, D/A converters, PLL, etc. A complete op amp is realized by combining analog circuit building blocks. The bipolar op-amp has the general purpose variety and is designed to fit a wide range of specifications. The terminal characteristics is nearly ideal.

4 SJTU Zhou Lingling4 The 741 Op-Amp Circuit General description The input stage The intermediate stage The output stage The biasing circuits Device parameters

5 SJTU Zhou Lingling5

6 6 General Description 24 transistors, few resistors and only one capacitor Two power supplies Short-circuit protection

7 SJTU Zhou Lingling7 The Input Stage The input stage consists of transistors Q1 through Q7. Q1-Q4 is the differential version of CC and CB configuration. High input resistance. Current source (Q5-Q7) is the active load of input stage. It not only provides a high-resistance load but also converts the signal from differential to single-ended form with no loss in gain or common-mode rejection.

8 SJTU Zhou Lingling8 The Intermediate Stage The intermediate stage is composed of Q 16, Q 17 and Q 13B. Common-collector configuration for Q 16 gives this stage a high input resistance as well as reduces the load effect on the input stage. Common-emitter configuration for Q 17 provides high voltage gain because of the active load Q 13B. Capacitor Cc introduces the miller compensation to insure that the op amp has a very high unit-gain frequency.

9 SJTU Zhou Lingling9 The Output Stage The output stage is the efficient circuit called class AB output stage. Voltage source composed of Q 18 and Q 19 supplies the DC voltage for Q 14 and Q 20 in order to reduce the cross-over distortion. Q 23 is the CC configuration to reduce the load effect on intermediate stage. Short-circuit protection circuitry  Forward protection is implemented by R 6 and Q 15.  Reverse protection is implemented by R 7, Q 21, current source(Q 24, Q 22 ) and intermediate stage.

10 SJTU Zhou Lingling10 The Output Stage (a) The emitter follower is a class A output stage. (b) Class B output stage.

11 SJTU Zhou Lingling11 The Output Stage  Wave of a class B output stage fed with an input sinusoid.  Positive and negative cycles are unable to connect perfectly due to the turn-on voltage of the transistors.  This wave form has the nonlinear distortion called crossover distortion.  To reduce the crossover distortion can be implemented by supplying the constant DC voltage at the base terminals.

12 SJTU Zhou Lingling12 The Output Stage  Q N and Q P provides the voltage drop which equals to the summer of turn-on voltages of Q N and Q P.  This circuit is call Class AB output stage.

13 SJTU Zhou Lingling13 The Biasing Circuits Reference current is generated by Q 12, Q 11 and R 5. Wilder current provides biasing current in the order of μA. Double-collector transistor is similar to the two- output current mirror. Q 13B provides biasing current for intermediate stage, Q 13A for output stage. Q 5, Q 6 and Q 7 is composed of the current source to be an active load for input stage.

14 SJTU Zhou Lingling14 Device Parameters For npn transistors: For pnp transistors: Nonstandard devices: Q 14 and Q 20 each has an area three times that of a standard device.

15 SJTU Zhou Lingling15 The Ideal Op Amplifier symbol for the op amp

16 SJTU Zhou Lingling16 The Ideal Op Amplifier The op amp shown connected to dc power supplies.

17 SJTU Zhou Lingling17 Characteristics of the Ideal Op Amplifier Differential input resistance is infinite. Differential voltage gain is infinite. CMRR is infinite. Bandwidth is infinite. Output resistance is zero. Offset voltage and current is zero. a)No difference voltage between inverting and noninverting terminals. b)No input currents.

18 SJTU Zhou Lingling18 Equivalent Circuit of the Ideal Op Amp

19 SJTU Zhou Lingling19 The Inverting Configuration  The inverting closed-loop configuration.  Virtual ground.

20 SJTU Zhou Lingling20 The Inverting Configuration

21 SJTU Zhou Lingling21 The Inverting Configuration

22 SJTU Zhou Lingling22 The Inverting Configuration Shunt-shunt negative feedback Closed-loop gain depends entirely on passive components and is independent of the op amplifier. Engineer can make the closed-loop gain as accurate as he wants as long as the passive components are accurate.

23 SJTU Zhou Lingling23 The Noninverting Configuration  The noninverting configuration.  Series-shunt negative feedback.

24 SJTU Zhou Lingling24 The Noninverting Configuration

25 SJTU Zhou Lingling25 The Voltage follower (a)The unity-gain buffer or follower amplifier. (b)Its equivalent circuit model.

26 SJTU Zhou Lingling26 The Weighted Summer

27 SJTU Zhou Lingling27 The Weighted Summer

28 SJTU Zhou Lingling28 A Single Op-Amp Difference Amplifier Linear amplifier. Theorem of linear Superposition.

29 SJTU Zhou Lingling29 A Single Op-Amp Difference Amplifier  Application of superposition  Inverting configuration

30 SJTU Zhou Lingling30 A Single Op-Amp Difference Amplifier Application of superposition. Noninverting configuration.

31 SJTU Zhou Lingling31 Integrators The inverting configuration with general impedances in the feedback and the feed-in paths.

32 SJTU Zhou Lingling32 The Inverting Integrators The Miller or inverting integrator.

33 SJTU Zhou Lingling33 Frequency Response of the integrator

34 SJTU Zhou Lingling34 The op-amp Differentiator

35 SJTU Zhou Lingling35 The op-amp Differentiator Frequency response of a differentiator with a time-constant CR.

36 SJTU Zhou Lingling36 The Antoniou Inductance- Simulation Circuit

37 SJTU Zhou Lingling37 The Antoniou Inductance- Simulation Circuit

38 SJTU Zhou Lingling38 The Op amp-RC Resonator An LCR second order resonator.

39 SJTU Zhou Lingling39 The Op amp-RC Resonator An op amp–RC resonator obtained by replacing the inductor L in the LCR resonator of a simulated inductance realized by the Antoniou circuit.

40 SJTU Zhou Lingling40 The Op amp-RC Resonator Implementation of the buffer amplifier K.

41 SJTU Zhou Lingling41 The Op amp-RC Resonator Pole frequency Pole Q factor

42 SJTU Zhou Lingling42 Bistable Circuit The output signal only has two states: positive saturation(L + ) and negative saturation(L - ). The circuit can remain in either state indefinitely and move to the other state only when appropriate triggered. A positive feedback loop capable of bistable operation.

43 SJTU Zhou Lingling43 Bistable Circuit  The bistable circuit (positive feedback loop)  The negative input terminal of the op amp connected to an input signal v I.

44 SJTU Zhou Lingling44 Bistable Circuit  The transfer characteristic of the circuit in (a) for increasing v I.  Positive saturation L + and negative saturation L -

45 SJTU Zhou Lingling45 Bistable Circuit The transfer characteristic for decreasing v I.

46 SJTU Zhou Lingling46 Bistable Circuit The complete transfer characteristics.

47 SJTU Zhou Lingling47 A Bistable Circuit with Noninverting Transfer Characteristics

48 SJTU Zhou Lingling48 A Bistable Circuit with Noninverting Transfer Characteristics The transfer characteristic is noninverting.

49 SJTU Zhou Lingling49 Application of Bistable Circuit as a Comparator Comparator is an analog-circuit building block used in a variety applications. To detect the level of an input signal relative to a preset threshold value. To design A/D converter. Include single threshold value and two threshold values. Hysteresis comparator can reject the interference.

50 SJTU Zhou Lingling50 Application of Bistable Circuit as a Comparator  Block diagram representation and transfer characteristic for a comparator having a reference, or threshold, voltage V R.  Comparator characteristic with hysteresis.

51 SJTU Zhou Lingling51 Application of Bistable Circuit as a Comparator Illustrating the use of hysteresis in the comparator characteristics as a means of rejecting interference.

52 SJTU Zhou Lingling52 Making the Output Level More Precise For this circuit L + = V Z 1 + V D and L – = –(V Z 2 + V D ), where V D is the forward diode drop.

53 SJTU Zhou Lingling53 Making the Output Level More Precise For this circuit L + = V Z + V D 1 + V D 2 and L – = –(V Z + V D 3 + V D 4 ).

54 SJTU Zhou Lingling54 Generation of Square Waveforms Connecting a bistable multivibrator with inverting transfer characteristics in a feedback loop with an RC circuit results in a square-wave generator.

55 SJTU Zhou Lingling55 Generation of Square Waveforms The circuit obtained when the bistable multivibrator is implemented with the positive feedback loop circuit.

56 SJTU Zhou Lingling56 Waveforms at various nodes of the circuit in (b). This circuit is called an astable multivibrator. Time period T = T 1 +T 2

57 SJTU Zhou Lingling57 Generation of Triangle Waveforms

58 SJTU Zhou Lingling58 Generation of Triangle Waveforms


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