UNIVERSITI MALAYSIA PERLIS

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1 UNIVERSITI MALAYSIA PERLIS ANALOG ELECTRONICS CIRCUIT II EKT 214 Semester II (2012/2013) EXPERIMENT # 3 OP-AMP (DIFFERENTIATOR & INTEGRATOR)

2 Analog Electronics II (EKT214) 2012/2013 EXPERIMENT 3 Op-Amp (Differentiator & Integrator) 1. OBJECTIVE: 1.1 To demonstrate the use of operational amplifier for performing differentiation and integration. 2. INTRODUCTION: 2.1 Differentiator A differentiator is a circuit that performs a calculus operation called differentiation. It produces an output voltage proportional to the instantaneous rate of change of the input voltage. Common applications of a differentiator are to detect leading and trailing edges of a rectangular pulse or to produce a rectangular output from a ramp input. input output Figure 2.1: Waveform of differentiator As shown in Figure 2.1, the output an electronic differentiator is proportional to the rate of change of the input waveform at any point in time. To perform differentiation, a capacitor is connected in series with the input as shown in Figure 2.2. The equation (2.1) can be used to determine the output voltage of the op-amp differentiator. v dvin( t) RC (2.1) dt o( t) The ideal differentiator is inherently unstable in practice due to the presence of some high frequency noise in every electronic system. An ideal differentiator would amplify this small noise. For instance, if v noise = Asin( t) is differentiated, the output would be v out = A cos( t). Even if A = 1 V, when = 2 10MHz) v out would have an amplitude of 63V! To circumvent this problem, it is traditional to include a series resistor at the input and a parallel capacitor across the feedback resistor as shown in 2

3 Analog Electronics II (EKT214) 2012/2013 Figure 2.3, converting the differentiator to an integrator at high frequencies for filtering. Figure 2.2: Ideal Differentiator 2.2 Integrator Figure 2.3: Practical Op-amp differentiator An integrator is a circuit that performs a mathematical operation called integration. The most popular application of an integrator is in producing a ramp of output voltage, which is linearly increasing or decreasing voltage. The integrator is sometimes called the Miller integrator, after the inventor. input output Figure 2.4: Waveform of integrator 3

4 Analog Electronics II (EKT214) 2012/2013 As shown in Figure 2.4, the output an electronic integrator is proportional to the total area under the input waveform up to that point in time. To perform integration, a capacitor is connected in the feedback path of the amplifier as shown in Figure 2.5. However, any dc voltage appearing at the input of an integrator will cause the output voltage to rise (or fall) until it reaches its maximum possible value. To prevent this undesirable occurrence, a resistor R F, is connected in parallel with the feedback capacitor as illustrated in Figure 2.6. Any dc input voltage, such as the input offset voltage of the amplifier, is then simply amplified by the dc gain, R F /R 1. Figure 2.5: Ideal Integrator Figure 2.6: Practical Op-amp integrator The equation (2.2) can be used to determine the output voltage of the operational amplifier integrator. t 1 vo( t) vin( t) dt vo (0) RC 0 (2.2) 4

5 Analog Electronics II (EKT214) 2012/ COMPONENT AND EQUIPMENT: 3.1 Resistors: k (1) k (1) kω (1) kω (2) 3.2 Capacitors: µF(1) 3.3 LM 741 OP-AMP 3.4 DC Power Supply 3.5 Oscilloscope 3.6 Function Generator 3.7 Breadboard 4. PROCEDURE: 4.1 Op-amp Differentiator Figure 4.1 shows an op-amp differentiator circuit. Construct a circuit on the breadboard. Apply a 5 khz, 1V pk sine wave input signal to the circuit. Complete TABLE 1 and record V in and waveforms on GRAPH 1 showing the amplitude and time. 22 k R F1 CH1 R S1 2.2 k C S µF CH2 V in Vout. CH1 gnd Figure 4.1 Op-Amp Differentiator Circuit CH2 gnd Apply a 20 khz, 1V pk sine wave input signal. Complete TABLE 2 and record V in and waveforms on GRAPH 2 showing the amplitude and time Now apply a 5 khz, 1V pk triangular wave input signal to the circuit. Complete TABLE 3 and record V in and waveforms on GRAPH 3 showing the amplitude and time. 5

6 Analog Electronics II (EKT214) 2012/ Op-amp Integrator Figure 4.2 shows an op-amp integrator circuit. Construct a circuit on the breadboard. Apply 5 khz, 1V pk sine wave input signal. Complete TABLE 4 and record V in and waveforms on GRAPH 4 showing the amplitude and time. 100 k R F2 CH1 10 k R S2 - + C F µF FF 741 CH2 V in R1 10 k CH1 gnd Figure 4.2 Op-Amp Integrator Circuit CH2 gnd Now, apply a 500 Hz, 1 V pk sine wave input signal to the circuit. Complete TABLE 5 and record V in and waveforms on GRAPH 5 showing the amplitude and time Apply a 5 khz, 1 V pk square wave input signal to the circuit. Complete TABLE 6 and record V in and waveforms on GRAPH 6 showing the amplitude and time. 6

7 Analog Electronics II (EKT214) 2012/2013 UNIVERSITI MALAYSIA PERLIS ANALOG ELECTRONICS 2 EKT 214 EXPERIMENT # 3 (DIFFERENTIATOR & INTEGRATOR) SEMESTER II (2012/2013) Name: PROGRAMME MATRIK # GROUP DATE 7

8 output voltage input Analog Electronics II (EKT214) 2012/ RESULTS: i) Op-amp Differentiator TABLE 1 V in (1 marks) OP-AMP DIFFERENTIATOR tim e GRAPH 1 (1 mark) 8

9 output voltage input Analog Electronics II (EKT214) 2012/2013 TABLE 2 R Vout R pre calc nominal F1 S V in measured R (2 marks) OP-AMP DIFFERENTIATOR tim e GRAPH 2 (1 mark) 9

10 voltage Analog Electronics II (EKT214) 2012/2013 dv Vout dt pre calc nominal TABLE 3 in C S R F1 measured R (2 marks) OP-AMP DIFFERENTIAT OR tim e GRAPH 3 (1 mark) 10

11 output voltage input Analog Electronics II (EKT214) 2012/2013 ii) Op-amp Integrator TABLE 4 V in (1 mark) OP-AMP INTEGRATOR tim e GRAPH 4 (1 mark) 11

12 output voltage input Analog Electronics II (EKT214) 2012/2013 R Vout R pre calc nominal,pk TABLE 5 F 2 S 2 V in measured R,pk (2 marks) OP-AMP INTEGRATOR tim e GRAPH 5 (1 mark) 12

13 voltage Analog Electronics II (EKT214) 2012/2013 Vout C pre calc nominal TABLE 6 F1 V R in S 2 2 f measured R (2 marks) OP-AMP INTEGRAT OR tim e GRAPH 6 (1 mark) 13

14 Analog Electronics II (EKT214) 2012/ QUESTIONS: (6 marks) 1. State the function of a differentiator. 2. What is the difference between a real differentiator and an ideal differentiator? 3. What does GRAPH 3 confirm the use of differentiator as a signal processor? CONCLUSIONS (8 marks) Based on your measurement data and graph, make an overall conclusion of differentiator and integrator op-amp. Differentiator is... Integrator is... 14