2. A compensating capacitor prevents
3. At the unity-gain frequency, the open-loop voltage gain is
4. The cutoff frequency of an op amp equals the unity-gain frequency divided by
5. If the cutoff frequency is 20Hz and the midband open-loop voltage gain is 1,000,000, the unity-gain frequency is
6. If the unity-gain frequency is 5 MHz and the midband open-loop voltage fgain is 100,000, the cutoff frequency is
7. The initial slope of a sine wave is directly proportional to
8. When the initial slope of a sine wave is greater than the slew rate,
9. The power bandwidth increases when
10. A 741C contains
11. A 741C cannot work without
12. The input impedance of a BIFET op amp is
13. An LF157A is a
14. If the two supply voltages are ±12V, the MPP value of an op amp is closest to
15. The open-loop curoff frequency of a 741C is controlled by
16. The 741C has a unity-gain frequency of
17. The unity-gain frequency equals the product of closed-loop voltage gain and the
18. If f_{unity} is 10 MHz and midband open-loop voltage gain is 200,000, then the open-loop curoff frequency of the op amp is
19. The initial slope of a sine wave increases when
20. If the frequency of the input signal is greater than the power bandwidth,
21. An op amp has an open base resistor. The output voltage will be
22. An op amp has a voltage gain of 200,000. If the output voltage is 1V, the input voltage is
23. A 741C has supply voltages of ±15V. If the load resistance is large, the MPP value is approximately
24. Above the cutoff frequency, the voltage gain of a 741C decreases approximately
25. The voltage gain of an op amp is unity at the
26. When slew-rate distortion of a sine wave occurs, the output
27. A 741C has
28. The closed-loop voltage gain of an inverting amplifier equals
29. The noninverting amplifier has a
30. The voltage follower has a
31. A summing amplifier can have
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---|---|---|---|---|---|---|---|---|---|
1 | d | 2 | b | 3 | a | 4 | b | 5 | d |
6 | a | 7 | b | 8 | a | 9 | b | 10 | c |
11 | c | 12 | d | 13 | d | 14 | d | 15 | d |
16 | c | 17 | c | 18 | c | 19 | b | 20 | a |
21 | c | 22 | b | 23 | c | 24 | d | 25 | b |
26 | b | 27 | d | 28 | c | 29 | c | 30 | a |
31 | b | ||||||||
2. what is thecommon-mode rejection ratio of an LF157A at low frequencies? Convert this decibel value to an ordinary number.
3. What is the open-loop voltage gain of an LF157A when the input frequency is 1kHz? 10kHz? 100kHz? (Assume a first-order response, that is, 20dB per decade rolloff.)
4. The input voltage to an op amp is a large voltage step. The output is an exponential waveform that changes 2.0V in 0.4us. What is the slew rate of the op amp?
5. An LM318 has a slew rate of 70V/us. What is the power bandwidth for a peak output voltage of 7V?
6. Use the equation f_{max} = S_{R} / 2 πV_{p} to calculate the power bandwidth for each of the following:
8. What is the output voltage in Fig.18-31 whaen v_{in} is zero? Use the typical values of Table 18-1.
Quantity | Symbol | Ideal | LM741C | LF157A |
---|---|---|---|---|
Open-loop voltage gain | A_{VOL} | Infinite | 100,000 | 200,000 |
Unity-gain frequency | f_{unity} | Infinite | 1MHz | 20MHz |
Input resistance | R_{in} | Infinite | 2MΩ | 10^{12}Ω |
Output resistance | R_{out} | Zero | 75Ω | 100Ω |
Input bias current | I_{in(bias)} | Zero | 80nA | 30pA |
Input offset current | I_{in(off)} | Zero | 20nA | 3pA |
Input offset voltage | V_{in(off)} | Zero | 2mV | 1mV |
common-mode rejenction ratio | CMRR | Infinite | 90dB | 100dB |
9. The data sheet of an LF157A lists the following worst-case parameters: I_{in(base)}=50pA, I_{in(off)}=10pA, and V_{in(off)}=2mV. Recalculate the output voltage when V_{in} is zero in Fig. 18-31.
11. What is the output voltage when V_{in} is reduced to zero in Fig. 18-32? Use the worst-case parameters given in Prob. 9.
13. What is the output voltage in Fig. 18-33b? The bandwidth?
14. The adjustable resistor of Fig. 18-34 can be varied from 0 to 100kΩ. Calculate the minimum and maximum closest-loop voltage gain and bandwidth.
15. Calculate the minimum and maximum closest-loop voltage gain and bandwidth in Fig. 18-35.
16. In Fig. 18-33b, the ac output voltage is 49.98mV. What is the closest-loop output impedance?
17. What is the initial slope of a sine wave with a frequency of 15kHz and a peak value of 2V? What happens to the initial slope if the frequency increases to 30kHz?
19. What is the CMRR of a 741C at 100kHz? The MPP value when the load resistance is 500Ω? The open-loop voltage gain at 1kHz?
20. If the feedback resistor in fig. 18-33a is changed to a 100kΩ variable resistor, what is the maximum output voltage? The minimum?
21. In Fig. 18-36, what is the closest-loop voltage gain for each switch position?
22. What is the closest-loop voltage gain for each switch position of Fig. 18-37? The bandwidth?
23. In wiring the circuit of Fig. 18-37, a technician leaves the ground off the 6kΩ resistor. What is the closest-loop voltage gain in each switch position?
24. If the 120kΩ resistor opens in Fig.18-37, what is the output voltage most likely to do?
25. What is the closest-loop voltage gain for each switch position of Fig. 18-38? The bandwidth?
26. If the input resistor opens in Fig.18-37, what is the closest-loop voltage gain for each switch position??
27. If the feeback resistor opens in Fig.18-38, what is the output voltage most likely to do?
28. The worst-case parameters for a 741C are I_{in(base)}=500nA, I_{in(off)}=200nA, and V_{in(off)}=6mV. What is the total output error voltage in Fig. 18-39?
29. In Fig. 18-39, the input signal has a frequency of 1kHz. What is the ac output voltage?
30. If the capacitor is shorted in fig. 18-39, what is the total output error voltage? Use the worst-case parameters given in prob. 28.
Use Fig. 18-40 for the remaining problems. A circuit like this is impractical for mass production because it has no feedback. The input offset positive or negative saturation. But assume that we have hand-selected a 741C to get a zero output error voltage for this theoritical exercise.
31. Predict the responses for each input base current.
32. Predict the responses for supply-voltage variations.
33. Predict the responses for slew-rate changes.
34. Predict the responses for peak-voltage changes.
increase | V_{1} | V_{2} | V_{in} | V_{out} | MPP | f_{max} |
---|---|---|---|---|---|---|
I_{B1} | ||||||
I_{B2} | ||||||
±V_{CC} | ||||||
S_{R} | ||||||
V_{p} | ||||||
1. | What is an ideal op amp? Compare the properities of a 741C to those of an ideal op amp. |
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2. | Draw an op amp with an input voltage step. What is slew rate, and why is it important? |
3. | Draw an inverting amplifier using an op amp with component values. Now, tell me where the virtual ground is. What are the properties of a virtual ground? What is the closest-loop voltage gain, input impedance, and bandwidth? |
4. | Draw a noninverting amplifier using an op amp with component values. Now, tell me where the virtual short is. What are the properties of a virtual short? What is the closest-loop voltage gain and bandwidth? |
5. | Draw a summing amplifier and tell me the theory of operation. |
6. | Draw a voltage follower. What are the closest-loop voltage gain and bandwidth? Describe the closest-loop input and output impedances. What good is this circuit if its voltage gain is so low? |
7. | What are the input and output impedances of a typical op amp? What advantage do these values have? |
8. | How does the frequency of the input signal to an op amp affect voltage gain? |
9. | The LM318 is a much faster op amp than the LM741C. In what applications might the 318 be preferred to the 741C? What are some possible disadvantages of using the 318? |
10. | With zero input voltage to an ideal op amp, why is there exactly zero output voltage? |
11. | Name a few linear ICs besides the op amp. |
12. | What condition is needed for an LM741 to produce maximum voltage gain? |
13. | Draw an inverting op amp and derive the formula for voltage gain? |
14. | Draw a noninverting op amp and derive the fomula for voltage gain. |
15. | Why is a 741C thought of as a dc or low-frequency amplifier? |