I'm using an NPN to pull a 12v (5mA) signal low from an MCU (logic level). My problem is that when I pull the 12v line low, 7.4v are still present at the 12v side of the line using the circuit below:
When I remove R2 and connect the signal directly to the collector pin on the NPN, about 110mV are still left on the line. See below:
Why isn't the NPN fully pulling the line low, and what can I do to fix it?
signal
will always be 12V, and your input!signal
will only control how hot your poor transistor gets. Are you sure this is what you intended to draw? \$\endgroup\$signal
. \$\endgroup\$