Elenco Electronics EP-130, Руководство пользователя

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We’re going to use the operational amplifier as a
Schmitt trigger circuit and as a comparator. The
operational amplifier produces a signal as long as its
input voltage exceeds a certain value. Look at the
schematic: can you see how it works? It shows that
the voltage level that causes the output to turn on is
higher then the voltage level that stops the output. It
looks like the Schmitt trigger circuit resists changing
the output state. We call such operation as
“hysteresis loop.”
Now, let’s get to the experiment. First leave the key
off. The operational amplifier works as a comparator
in this state. When you rotate the control, LEDs 1
and 2 take turns lighting at some point. Note that this
point doesn’t change whether you turn the control
clockwise or counterclockwise.
Now, press the key on, and you’ll have a Schmitt
trigger circuit that produces hysteresis loops, as
shown in Figure 1.
The width of hysteresis becomes narrower as the
RB/RA increases. Notice how the width changes
when using different values for RA and RB.
Notes:
EXPERIMENT #74: SCHMITT TRIGGER CIRCUIT
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Wiring Sequence:
o
70-36-26-121
o
27-83
o
63-28-130-131
o
34-33-67-90
o
68-134
o
84-69-138
o
89-137
o
119-124-135
o
122-132
o
31-129
Schematic