Education –
Introduction to
the Optocoupler

It is a small device that allows
... the transmission of a signal
between parts of a circuit
while keeping those two
parts electrically isolated. How
is this so? Inside our typical optocoupler are two things –
an LED and a phototransistor.
When a current runs through
the LED, it switches on - at
which point the
phototransitor detects the light and allows another
current to flow through it.
And then when the LED is off,
current cannot flow through
the phototransistor. All the
while the two currents are completely electrically isolated
(when operated within their
stated parameters!)