Differences

This shows you the differences between two versions of the page.

--- 2019_cargo_present_sensor [2019/02/24 22:41] – [An inverter with one transistor] tell
+++ 2019_cargo_present_sensor [2019/02/24 22:51] (current) – [combining open-drain outputs to make a logic gate] tell
@@ Line 88: / Line 88: @@
 Instead of pullup resistors, we can use a resistor in series with an LED.  In fact, we can connect the output of this gate to one of our [[DIO tester and breakout]] boards.
+If we build anything with mosfets as a standalone board, we never want to connect a mosfet gate only to an input connector (as drawn above for clarity).  The input resistance of a fet gate is so high that can stay charged to either a logic high or low or somewhere in between.  We always want to use either a pullup or pulldown resistor on a mosfet gate that would otherwise connect only to an off-board connector.  Of course, if an LED is also connected to that input, it will serve to pull the mosfet gate to a defined value.  Merging this gate circuit into the DIO tester board would also do that.