Chapter Questions
What type of feedback is applied to an op amp when an external component is connected between the output terminal and the inverting input?
If the open-loop gain is very large, does the closed-loop gain depend on the external components or the op amp?
What two assumptions have been used to analyze the circuits in this chapter?
Identify the circuit in Fig. P3-4.
Calculate $V_o$ and the op amp's output current in Fig. P3-4 if $E_1$ equals (a) $+5 \mathrm{~V}$; (b) $-2 \mathrm{~V}$. For each situation, state if the op amp sources or sinks current.
Calculate $E_i$ in Fig. P3-4 if $V_o$ equals (a) $+5 \mathrm{~V}$; (b) $-2 \mathrm{~V}$.
Let $E_i$ be a triangle wave with a frequency of $100 \mathrm{~Hz}$ and a peak value of $5 \mathrm{~V}$ in Fig. P3-4.(a) Plot $E_i$ and $V_o$ vs. time; (b) $V_o$ vs. $E_i$.
Repeat Problem 3-7 but let $E_i$ be increased in amplitude to $8 \mathrm{~V}$. (Assume $\pm V_{s a t}= \pm 15 \mathrm{~V}$ for ease of plotting.)
Identify the circuit in Fig. P3-9 and calculate $V_o$ if $E_i$ equals (a) $+5 \mathrm{~V}$; (b) $-2 \mathrm{~V}$. Compare your results with Problem 3-5.
Repeat Problem 3-7 except apply it to Fig. P3-9. Compare solutions of both problems to distinguish between inverting and noninverting operation.
Design an inverting amplifier with a gain of -5 and an input resistance of $10 \mathrm{k} \Omega$.
Design a noninverting amplifier with a gain of 5 .
Input-output characteristics are shown for three different circuits in Fig. P3-13. Design circuits to re-create plots $A, B$, and $C$.
The circuit of Fig. P3-14 is called a "subtractor." Is $E_1$ subtracted from $E_2$, or vice versa?
A 5-V peak-to-peak sine wave, $E_2$, is applied to the summing node in Fig. P3-14. Plot $V_o$ vs. $E_1$ if voltage $E_1$ is (a) $+5 \mathrm{~V}$; (b) $-5 \mathrm{~V}$.
A 5-V peak-to-peak sine wave, $E_i$, is applied to (+) In of Fig. P3-15. Plot $V_w$ vs. $E_i$ if the voltage of (-) In is (a) $+5 \mathrm{~V}$; (b) $-5 \mathrm{~V}$. (Assume that $\pm V_{\text {sat }}= \pm 15 \mathrm{~V}$.)
Design a three-channel inverting amplifier. Gains are to be -1 for channel $1,-3$ for channel 2, and -5 for channel 3 (refer to Section 3-3.2).
Design a two op amp circuit to subtract I V from $3 \mathrm{~V}$. Show the output voltage present at each op amp.
Design a circuit to amplify the difference between $E_1$ and $E_2$ by 5 . The inputs $E_1$ and $E_2$ should be buffered.
Redesign the system of Fig. 3-20 to measure a temperature range from $0^{\circ}$ to $100^{\circ} \mathrm{C}$.
Obtain the data sheet of the LM135/335 temperature sensor from National Semiconductor's Web site and determine(a) temperature range (continuous) of the LM135.(b) temperature range (continuous) of the LM335.(c) package styles of the LM335.(d) operating current range.(e) LM335 temperature accuracy (typical) at $25^{\circ} \mathrm{C}$.