I have a strange behavior with the circuit below.
(the bidirectional logica level should be read as:
- VL = Voltage Low
- GNDL = GND Low
- VH = Voltage High
GNDH = GND High
L1 = Low channel 1 (I did only draw 1 for simplicity, there are 4 in total)
- H1 = High channel 1
This is the level shifter:
- When the switch is open:
- 1.98 V between GND and L1 (of the shifter)
- 4.57 V on the gate of the Mosfet
- LED is on
- When the switch is closed:
- 3.30 V between GND and L1 (of the shifter)
- 5.26 V on the gate of the Mosfet
- LED is on
Of course the LED is always on since the gate voltage is in both cases high enough.
How can there be 1.98 V between GND and L1 while the switch is open (I assume the gate does not return any voltage) and 4.57 on the gate?
- When I change the 10 KOhm resistor by a 200 ohm, the LED works as expected (on when closed, off when opened).
- Without the level shifter and using 5 V for the entire circuit, also the LED works as expected
- Without the level shifter and using the 3.3 V than the 2N7000 does not get enough voltage on the gate (therefore I want to use the shifters, at least until I receive my better mosfet, IRL44N).