OPAMP integrator & differentiator.pptx

opamp

1. OPERATIONAL AMPLIFIER AS INTEGRATOR AND DIFFERENTIATOR DEPARTMENT OF PHYSICS PRESENTED BY JATIN MAHATO (1801168007) SUPRIYA NAYAK (1801168017) 28-02-2020 1

2. CONTENTS OPERATIONAL AMPLIFIER IC 741 OP-AMP INTEGRATOR DRAWBACKS IN IDEAL INTEGRATOR PRACTICAL INTEGRATOR FREQUNCY RESPONSE APPLICATION IDEAL DIFFERENTIATOR PRACTICAL DIFFERENTIATOR FREQUENCY RESPONSE APPLICATION REFERENCES 28-02-2020 2

3. An  Operational Amplifier , or op-amp for short, is fundamentally a voltage amplifying device designed to be used with external feedback components such as resistors and capacitors between its output and input terminals. These feedback components determine the resulting function or “operation” of the amplifier and by virtue of the different feedback configurations whether resistive, capacitive or both, the amplifier can perform a variety of different operations, giving rise to its name of “Operational Amplifier”. WHAT IS OP AMP 28-02-2020 3

4. The 741 Op Amp IC is a monolithic integrated circuit, comprising of a general purpose Operational Amplifier. It was first manufactured by Fairchild semiconductors in the year 1963. The number 741 indicates that this operational amplifier IC has 7 functional pins, 4 pins capable of taking input and 1 output pin. IC 741 Op Amp can provide high voltage gain and can be operated over a wide range of voltages, which makes it the best choice for use in integrators, summing amplifiers and general feedback applications . IC-741 28-02-2020 4

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6. OP-AMP INTEGRATOR   Op-amp Integrator  is an operational amplifier circuit that performs the mathematical operation of  Integration , that is we can cause the output to respond to changes in the input voltage over time as the op-amp integrator produces an  output voltage which is proportional to the integral of the input voltage . 28-02-2020 6

7.       From fig , current through the resistor R, Due to the virtual ground, i = i c 28-02-2020 7 Since the open loop gain and the input impedance of the are infinite A point may be treated as virtual ground. The current through the feedback capacitor C, Where q=C(0-V o )

8. Drawbacks in ideal integrator For dc input (f = 0), reactance of capacitance, Xc is infinite. Because of this op-amp goes into open loop configuration.In open loop configuration the gain is infinite and hence the small input offset voltages are also amplified and appears at output as error. This is referred as false triggering and must be avoided. Bandwidth is very small and used for only small range of input frequencies. Due to all such limitations, an ideal integrator needs to be modified.

9. CIRCUIT DIAGRAM OF PRACTICAL INTEGRATOR 28-02-2020 9 The limitations of an ideal integrator can be minimized in the practical circuit by adding resistor Rf in parallel with capacitor C this Rf avoids op-amp going into open loop configuration at low frequencies. The addition of Rf will fix the low frequency gain (A) of the circuit to a fixed small value and so the input offset voltage will have practically no effect on the output offset voltage and variations in the output voltage is prevented.

10. FREQUENCY RESPONSE OF INTEGRATOR 28-02-2020 10 f a f b Frequency(Hz) |A| in db At f<fa , opamp acts as inverting opamp . To use the opamp as integrator, input signal should have freq. > fa the true integration is possible over the range fa < f < fb. f a =1/(2πR f C) , cut off frequency fb=1/2 πRC , unit gain frequency Where,

11. Square Wave Sine Wave Step signal

12. APPLICATIONs OF INTEGRATOR analog-to-digital(A-D) converters ramp generators wave shaping applications. Digital voltmeters Op-amp integrating amplifiers are used to perform calculus operations in analogue computers. 28-02-2020 12

13. OP-AMP DIFFERENTIATOR An op amp differentiator is basically an inverting amplifier with a capacitor of suitable value at its input terminal, performs the mathematical operation of  Differentiation , that is it “ produces a voltage output which is directly proportional to the input voltage’s rate-of-change with respect to time ’’ . 28-02-2020 13

14. 28-02-2020 14 CIRCUITAL ANALYSIS As we can see from the figure that all the input current Ic flows through the feedback resistor R i.e Eq (I) shows that the output is the differentiation of the input with an iversion and a scale multiplier of RC.

15. PRACTICAL DIFFERENTIATOR For an ideal differentiator, the gain increases as frequency increases. Thus, at some higher frequencies, the differentiator may become unstable and cause oscillations which results in noise. These problems can be avoided or corrected in a practical differentiator circuit which uses a resistor R1 in series with the input capacitor and a capacitor Cf in parallel with the feedback resistor. 28-02-2020 15

16. FREQUENCY RESPONSE OF PRACTICAL DIFFERENTIATOR The gain of an op-amp differentiator is directly dependent on the frequency of the input signal. Hence, for DC inputs where f = 0, the output is also zero. As the frequency of the input signal increases, the output also increases. The frequency f 1  is the frequency for which the gain of the differentiator becomes unity. It can be seen from the figure that for frequency less than f 1 , the gain is less than unity. For f 1 , the gain becomes the unity (0 dB) and beyond f 1 , the gain increases at 20dB per decade 28-02-2020 16

17. The sine wave is converted to a cosine waveform - giving 90° of phase shift of the signal A fast change to the input voltage signal, the greater the output voltage change in response. The square wave input, only very short spikes should be seen. The spikes will be limited by the slope of the edges of the input waveform and also the maximum output of the circuit and its slew rate and bandwidth. The triangular wave input transforms to a square wave in line with the rising and falling levels of the input waveform. 28-02-2020 17

18. APPLICATION OF DIFFERENTIATOR to operate on triangular and rectangular signals. wave shaping circuits, to detect high frequency components in the input signal. Differentiators have frequency limitations while operating on sine wave inputs; the circuit attenuates all low frequency signal components and allows only high frequency components at the output. In other words, the circuit behaves like a high-pass filter. 28-02-2020 18

19. REFERENCES GOOGLE IMAGES ELECTRONICS 4U ELECTRONICSHUB ELECTRONICS TUTORIALS FUNDAMENTAL ELECTRONICS BY V.K MEHETA ELECTRINICS BOOK BY B.S GHOSH 28-02-2020 19

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