Hello,
In my project i have to switch two P-mosfets (5V on source) with one 3.3V signal.
What is the best way to do that with only transistors and resistors?
Probably option no. 5, but it needs 2 transistors (space on PCB).
Can't I just got with 1/2/3?
I attach schemtics.
#5 works for me. You don't need R19 or R24 if you're looking to save parts.
I know that would work best, but I'm looking to cut on active parts. The best for me would be one transistor, because there would be less probability of failure.
All circuits turn the mosfets off slowly, because of the <250uA gate pull up current (22k resistor).
That could be a problem if you switch high currents.
How much current, why the two fets.
Resistor from base to ground (R26) is nonsense. Remove.
Use the third diagram on this page.
Connect the two gates and the two sources together if you must use two fets.
Leo..
IF you need them to switch and recover at identical times, you need to get them from the same lot number or actually selectively match then. The gate capacitance will vary, affecting the timing.
Paul
I'm not switching high currents. Max is like 20mA.
Two Mosfets because two outpus signals are connected to each drain (I can't connect them together, because whole system won't work).
I don't need low switching times and allowed difference is up to 5ms.
I put resistor from base to ground to ground base if atmega won't turn on.
