Page 52 - Op Amps Design, Applications, and Troubleshooting

Review Questions 35

5. If three 10-megohm resistors were connected in series across a 10-volt power supply
and one of the resistors became open, would this open have much effect (e.g., >5%) on
the currents in the remaining resistors?
6. What is the effect (significant or negligible) on total current if the resistors described in
Question 5 are all connected in parallel with the power source?
7. If two 10-megohm resistors are connected in parallel with a 1,0-kilohm resistor,
explain the relative effect on total current if one of the 10-megohm resistors opens.
Repeat this question for the case where the 1.0-kilohm resistor develops an open.
8. If zero volts is applied directly to the inverting input of an ideal op amp at the same
time that -0.1 volts is applied to the noninverting input, compute or describe the value
of the output voltage.
9. If a portion of an op amp's output signal is returned to its input (i.e., feedback), we say
that the amplifier is operating -loop.
10. What is the value of each of the following parameters for an ideal op amp?
a. Bandwidth
b. Input current
c. Open-loop voltage gain
d. Input impedance
e. Lowest operating frequency
f. Highest operating frequency
g. Slew rate
h. Output impedance
i. Common-mode voltage gain
11. Can a real (i.e., practical) op amp be used to amplify DC?
12. If the largest output voltage swing for a particular 741 design is ±5 volts, what is the
highest sinewave frequency that can be amplified before slew rate limiting begins to
distort the output? (Assume a slew rate of 0.5 V///s.)
Refer to Appendix 1 for questions 13 to 15.
13. What is the open-loop voltage gain of a standard 741 op amp at a frequency of 2 hertz
(interpret the graphical data)?
14. What is the minimum input resistance of a 741 op amp?
15. What is the approximate open-loop voltage gain of a standard 741 op amp at a
frequency of 100 kilohertz (interpret the graphical data)?