I was looking around at some other questions that were asked dealing with how to use an LED to indicate UART activity. One of them provided the image below, however it was stated in the comments that factors such as cable length and baud rate will cause significant signal degradation.
Other questions recommended using a MOSFET to drive the LED instead. I haven't dealt with those before and wanted to confirm some of the specifications before proceeding.
When choosing a MOSFET for this portion of my circuit I came across the BSS138 N-Channel on DigiKey and the specs I don't exactly understand/want to confirm are adequate are:
- Current - Continuous Drain (Id) @ 25°C: 200mA (Ta)
- Drive Voltage (Max Rds On, Min Rds On): 2.75V, 5V
- Vgs(th) (Max) @ Id: 1.5V @ 1mA
These are my own interpretations for the three items:
- Current: The maximum current that the MOSFET can switch.
- Vgs(th): The threshold to switch the MOSFET (<1.5V: Off, >1.5V: On).
- Drive Voltage (Max Rds On, Min Rds On): This is one I just really do not understand.
With that being said would the BSS138 be suitable for the following circuit and not have any major affect on the communications?