3-29
Q-20.
In a closed-loop configuration the output signal is determined by (the input signal, the feedback
signal, both).
Q-21.
In the inverting configuration, the input signal is applied to the (a) (inverting, noninverting)
input and the feedback signal is applied to the (b) (inverting, noninverting) input.
Q-22.
In the inverting configuration, what is the voltage (for all practical purposes) at the inverting
input to the operational amplifier if the input signal is a 1-volt, peak-to-peak sine wave?
Q-23.
In the inverting configuration when the noninverting input is grounded, the inverting input is at
(signal, virtual) ground.
Q-24.
In a circuit such as that shown in figure 3-15, if R1 has a value of 100 ohms and R2 has a value
of 1 kilohm and the input signal is at a value of + 5 millivolts, what is the value of the output
signal?
Q-25.
If the unity-gain point of the operational amplifier used in question 24 is 500 kilohertz, what is
the bandwidth of the circuit?
Q-26.
In a circuit such as that shown in figure 3-16, if R1 has a value of 50 ohms and R2 has a value of
250 ohms and the input signal has a value of +10 millivolts, what is the value of the output
signal?
Q-27.
If the open-loop gain of the operational amplifier used in question 26 is 200,000 and the open-
loop bandwidth is 30 hertz, what is the closed loop bandwidth of the circuit?
APPLICATIONS OF OPERATIONAL AMPLIFIERS
Operational amplifiers are used in so many different ways that it is not possible to describe all of the
applications. Entire books have been written on the subject of operational amplifiers. Some books are
devoted entirely to the applications of operational amplifiers and are not concerned with the theory of
operation or other circuits at all. This module, as introductory material on operational amplifiers, will
show you only two common applications of the operational amplifier: the summing amplifier and the
difference amplifier. For ease of explanation the circuits shown for these applications will be explained
with d.c. inputs and outputs, but the circuit will work as well with a.c. signals.
Summing Amplifier (Adder)
Figure 3-20 is the schematic of a two-input adder which uses an operational amplifier. The output
level is determined by adding the input signals together (although the output signal will be of opposite
polarity compared to the sum of the input signals).
