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EKT 214 ANALOG ELECTRONIC CIRCUIT II SEM II 2012/2013 TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY RESPONSE QUESTION 1. Describe briefly the following terms as applied to an ideal operational amplifier: i) iii) v) vii) 2. Virtual ground; Input dc offset voltage; Input bias current; Slew rate. ii) iv) vi) Virtual short; Output dc offset voltage; Input offset current; List down five parameters of an op-amp and give comparisons between an ideal and a practical opamp with regards to these parameters and hence draw the equivalent circuit of an ideal op-amp and a simplified equivalent circuit of a practical op-amp. 3. With the aid of suitable diagrams, give brief description of the terms DIFFERENTIAL MODE INPUT and COMMON-MODE INPUT as applied to an op-amp and hence give the mathematical definition for the term COMMON-MODE REJECTION RATIO (CMRR). 4. Consider an operational amplifier with ideal parameters and the op-amp is operated as an inverting constant gain multiplier with the input signal voltage V1 applied through R1 and the output signal Vo is fed back to the input through RF. a) Draw the circuit diagram. b) Draw the ac equivalent circuit for practical op-amp, ideal op-amp and redrawn the equivalent circuit. c) Prove that the gain is controlled by š š¹ & š 1 using superposition theorem and appropriate equivalent circuit. 1 EKT 214 ANALOG ELECTRONIC CIRCUIT II SEM II 2012/2013 TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY RESPONSE 5. Consider an operational amplifier in Figure 1 with ideal parameters and the op-amp is operated as non-inverting constant gain multiplier. b) Draw the ac equivalent circuit. c) Prove that the gain is A ļ½ 1 ļ« RF using voltage divider rule. R1 Figure 1 6. Perform an ac analysis on the circuit in Figure 2 to obtain an expression for the voltage gain Av where; Av ļ½ vO vI 2 Figure 2 EKT 214 ANALOG ELECTRONIC CIRCUIT II SEM II 2012/2013 TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY RESPONSE 7. The inverting amplifier in Figure 3 receives an input signal from the source vs. The source is capable of delivering a maximum current of 4 ļA at a peak voltage of 0.2 V. Design the amplifier for a gain |Av| of 20. Assume that the op-amp is ideal. Figure 3 8. Calculate the output voltage V2 & V3 based from Figure 4. Figure 4 3 EKT 214 ANALOG ELECTRONIC CIRCUIT II SEM II 2012/2013 TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY RESPONSE 9. Determine the output voltage of the DAC in Figure 5(a). The sequence of 4 digit binary codes represented by the waveforms in Figure 5(b) are applied to the inputs. A high level is a binary 1, and a low level is a binary 0. The least significant binary digit is D0. Draw a graph of binary input versus Vout. Figure 5 10. Based from Figure 6, find the output voltage, Vout and illustrate the respective equivalent circuit when the binary input is 0001. Figure 6 4 EKT 214 ANALOG ELECTRONIC CIRCUIT II SEM II 2012/2013 TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY RESPONSE 11. For the circuit in Figure 7; a) derive the expression for the output voltage vO in terms of the input voltages vI1 and vI2, and the circuit parameters R1, R2, R3, and R4; b) Show that under certain condition, the output voltage vO is proportional to the difference of the input voltages vI1 and vI2 and determine the constant of proportionality under this condition. R2 vI1 R1 vO R3 vI2 + R4 Figure 7 12. Design the circuit in Figure 8(a) to produce an output voltage vO in Figure 8(c) when the input voltage vI is as shown in Figure 8(b). Assume the op-amp is ideal and use C = 220 pF. Figure 8(a) 5 EKT 214 ANALOG ELECTRONIC CIRCUIT II SEM II 2012/2013 TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY RESPONSE Figure 8(b) Figure 8(c) 13. For the circuit in Figure 9(a), C = 0.1 ļF and R = 10 kļ. Both the output and input voltages are zero at t = 0. An input voltage vI shown in Figure 9(b) is applied to the circuit. Sketch the resulting output waveform vO(t). Figure 9(a) 6 EKT 214 ANALOG ELECTRONIC CIRCUIT II SEM II 2012/2013 TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY RESPONSE Figure 9(b) 14. The input signal in Figure 10(a) is applied to the comparator in Figure 10(b). Draw the output showing its proper relationship to the input signal. Assume the maximum output levels of the comparator are ±14š. Figure 10 7 EKT 214 ANALOG ELECTRONIC CIRCUIT II SEM II 2012/2013 TUTORIAL 1 – OPERATIONAL AMPLIFIER & OP-AMP APPLICATION & FREQUENCY RESPONSE 15. Determine the output voltage waveform for Figure 11. (Hint: Find the values of upper trigger point (UTP) and the lower trigger point (LTP)). Figure 11 8