Guys I have a tiny mosfet in circuit “2300” gate opens to the 7.4v signal out of a main controller, when mosfet opens it will ground it. (Small mcu send trigger signal to open / close it)
How ever I tested it on two cases:
gate on a controller that has 4.5v, and mosfet grounds it to 0v no issue
gate on a controller that has 7.4v (don’t ask me why), and mosfet grounds it with 1.15v remaining 
Why is that and how can it be grounded but not fully?
Hi, @yoodog
Welcome to the forum.
What is the supply to the load, R3?
Is the supply to R3 sharing the same gnd as Q1 and the device providing the gate voltage?
Tom.. 
Hi, yes ground is common. R3 is in line though on a trigger output of my MCU.
I don’t get why 4.5v gave signal gets fully grounded vs 7.4v (strange controller signal voltage though) gets down only to 1.5v
So why are you trying to pull it down to ground if there is an OUTPUT at "Trigger"?
Why are you applying 7.4V?
What is the device?
Please explain what you are trying to do?
Thanks.. Tom..
My friend told me that signal line is pushing too many ma, about 100x more than expected (usually 0.5ma, no 50ma!)
If you really need to know what it is, basically I have a mcu that based on digital input should close mosfet to ground a E-Brake signal on escooter controller (emulating a mechanical brake lever that has built in switch inside that closes loop to the gnd when engaged)
4.5v is in one brand scooter
7.4v is on another brand scooter, after remain 1.15v
In either case, you have your signals mixed-up.
Brake out = TRIGGER (the gate)
4.5/7.7 = COMMON BRAKE (the drain)
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