Experiment 1 - The Voltage Regulator
How do you connect the 78xx?
Here you get to know a simple circuit using a 7805...
Consider the circuit shown...
is connected to the positive pole of the battery.
is connected to the negative pole (zero potential) of the battery.
At Pin 3
a voltage of 5.0 Volt is present.
The light emitting diode LED1 lights up.
In order to limit the current through LED1
to 20 mA, you use a resistor of 150 Ω....
Circuit diagram voltage regulation with the 7805.
Circuit voltage regulation with the 7805.
With a multimeter you can easily convince yourself
that the voltage
Vout = 5 Volt...
Circuit diagram measurement of the voltage Vout of the 7805.
Circuit measurement of the voltage Vout of the 7805.
The tolerance of a typical 7805 is 4% (see the datasheet).
The voltage Vout
can therefore differ by 0.2 Volt up or down.
But what happens to the voltage regulator
at a higher input voltage
or under load...?