I am supposed to simulate this circuit (regulated power supply 5V), however I am not understanding what's the point of the resistor R. Is it a load resistor? Cause i thought these needed to be before the regulator.
\$\begingroup\$
\$\endgroup\$
2
-
4\$\begingroup\$ yes. it's a load resistor. \$\endgroup\$– Marko BuršičApr 1, 2020 at 18:08
-
1\$\begingroup\$ @KingDuken: I don't see anything to do with current regulation in the OP's schematic. \$\endgroup\$– Peter BennettApr 1, 2020 at 19:06
Add a comment
|
2 Answers
\$\begingroup\$
\$\endgroup\$
If you look at a typical 7805 datasheet you'll find a statement like
Note: Minimum load current for regulation is 5 mA
If the circuit is expected to maintain a 5V output with a load going right down to zero, the resistor R ensures that enough current is drawn from the 7805 to guarantee that the 5mA minimum is met. In this case a 1000 Ohm resistor would be needed.
It's often not seen in the real world because the 7805 will normally be built into a circuit that will always take at least the minimum load.
\$\begingroup\$
\$\endgroup\$
As you adjust \$R\$ in your simulation, you should be able to see the input voltage (across \$C\$) go up or down, but the voltage across \$R\$ should remain relatively constant.
