For this section you will need some basic knowledge
about the operational amplifier integrated circuit.
First, we can use one power source for both the
circuit and the IC, or we can use separate power
sources.
The operational amplifier can be used as a non-
inverting amplifier, an inverting amplifier, or a
differential amplifier. A non-inverting amplifier
reproduces an input signal as an output signal
without any change in polarity. An inverting amplifier
does the opposite: its output has the reverse polarity
of its input. The differential amplifier has an output
that is the difference between the strengths of the
two input signals.
A comparator compares two voltages and tells you
which one is stronger than the other. We call the
controlled voltage the reference voltage because we
use it as a reference for measuring other voltages.
The voltage that is compared is the input voltage.
The reference voltage in this project is about 3.7V. It
is connected to terminal 68 of one of the integrated
circuits. Input voltage flows to terminal 69 of the
same IC. The LED lights if this voltage is higher than
the reference voltage, and stays off if it is lower. In
this circuit the operational amplifier acts as an
inverting amplifier for the reference voltage to keep
the LED turned off, or as a non-inverting amplifier to
light the LED.
Build the project and then set the switch to position
A. This provides an input of 6V. The LED lights
because the input voltage is higher than the
reference voltage. Now slide the switch to position B.
This provides an input voltage of 1.5V. The
comparator IC does not let the current pass because
the input voltage is now lower than the reference
voltage – the LED remains off.
Notes:
EXPERIMENT #70: COMPARATOR
Schematic
-89-
Wiring Sequence:
o
31-67
o
84-82-33-70-121
o
63-122
o
68-83-78
o
69-81-76
o
75-132
o
77-119-124
o
120-133
o
123-131
Содержание EP-130
Страница 11: ... 11 I ENTERTAINMENT CIRCUITS ...
Страница 26: ... 26 II BASIC SEMICONDUCTOR AND COMPONENTS CIRCUITS ...
Страница 36: ... 36 III LED DIGITAL DISPLAY CIRCUITS ...
Страница 41: ... 41 IV A TOUR THROUGH DIGITAL CIRCUITS ...
Страница 49: ... 49 V MORE ADVENTURES WITH DIGITAL CIRCUITS ...
Страница 64: ... 64 VI THE WORLD OF TRANSISTOR TRANSISTOR LOGIC ...
Страница 77: ... 77 VII APPLICATION CIRCUITS BASED ON THE OSCILLATOR ...
Страница 88: ... 88 VIII BASIC OPERATIONAL AMPLIFIER CIRCUITS ...
Страница 116: ... 116 IX MORE ADVENTURES WITH OPERATIONAL AMPLIFIERS ...
Страница 129: ... 129 X COMMUNICATION CIRCUITS ...
Страница 136: ... 136 XI TESTING AND MEASURING CIRCUITS ...