3-15
Q-8. If the differential amplifier is configured with a single input and differential outputs, what will
the output signals be?
Q-9. If the single-input, differential-output, differential amplifier has an output signal taken between
the two output terminals, what will the peak-to-peak amplitude of this combined output be?
In answering Q10 through Q14 use the following information: A differential amplifier is configured
with a differential input and a differential output. All input signals are sine waves with a peak-to-peak
amplitude of 10 millivolts. The gain of the differential amplifier is 10.
Q-10. If the input signals are in phase, what will be the peak-to-peak amplitude of the output signals?
Q-11. If the input signals are 180 degrees out of phase with each other, what will be the peak-to-peak
amplitude of the output signals?
Q-12. If the input signals are 180 degrees out of phase with each other, what will the phase
relationship be between (a) the output signals and (b) the input and output signals?
Q-13. If the input signals are 180 degrees out of phase with each other and a combined output is taken
between the two output terminals, what will the amplitude of the combined output signal be?
Q-14. If the input signals are 90 degrees out of phase with each other and a combined output is taken
between the two output terminals, (a) what will the peak-to-peak amplitude of the combined
output signal be, and (b) will the combined output signal be a sine wave?
OPERATIONAL AMPLIFIERS
An OPERATIONAL AMPLIFIER (OP AMP) is an amplifier which is designed to be used with
other circuit components to perform either computing functions (addition, subtraction) or some type of
transfer operation, such as filtering. Operational amplifiers are usually high-gain amplifiers with the
amount of gain determined by feedback.
Operational amplifiers have been in use for some time. They were originally developed for analog
(non-digital) computers and used to perform mathematical functions. Operational amplifiers were not
used in other devices very much because they were expensive and more complicated than other circuits.
Today many devices use operational amplifiers. Operational amplifiers are used as d.c. amplifiers,
a.c. amplifiers, comparators, oscillators (which are covered in NEETS, Module 9), filter circuits, and many
other applications. The reason for this widespread use of the operational amplifier is that it is a very
versatile and efficient device. As an integrated circuit (chip) the operational amplifier has become an
inexpensive and readily available "building block" for many devices. In fact, an operational amplifier in
integrated circuit form is no more expensive than a good transistor.
CHARACTERISTICS OF AN OPERATIONAL AMPLIFIER
The schematic symbols for an operational amplifier are shown in figure 3-10. View (A) shows the
power supply requirements while view (B) shows only the input and output terminals. An operational
amplifier is a special type of high-gain, d.c. amplifier. To be classified as an operational amplifier, the
circuit must have certain characteristics. The three most important characteristics of an operational
amplifier are:
