Conversion from 24V input to NPN or PNP output

[Yaroooo]

I've made a small circuit to accomplish this function:

• An input signal of max. 10kHz frequency is applied to RX;
• Input signal can have a voltage between 5v to 24v, but for first analysis I've assumed 24v;
• Two functions can be set, NPN output or PNP output based on Jumpers (JP) configuration where JPn is open and !JPn is closed;

R3, R4, R5, R6 are voltage dividers to protect Gate;

What is my problem:

• Connecting RX to +24V or GND actually doesn't work either in NPN or PNP configurations. Output is fix to 23,39V.
• Circuit starts to work removing R4 and R6, but not as expected. In PNP configuration I've:
• 4,76V (RX to GND) and 23,21V (RX to 24V)
• In NPN configuration I've:
• 23,22V (RX to GND) and 4,66V (RX to 24V)

In this two case I don't have a completely working circuit. With voltage dividers, output doesn't work. Without them, gate is not protected and also output never reach 0V (as it should).

Can you kindly provide me tips about what is wrong?

Unfortunately I've already ordered printed circuits without performing a breadboard test before that (I know, my error). If there's a way to solve the problem using already present pads would be the best, anyway I'd like just to solve the problem.

BOM is:
Q1, Q2 - 2N7000TA
Q3 - VP2106N3-G

P.S. As PNP and NPN I'm meaning (maybe wrongly) an inverted and non-inverted output. Not industrial source/sink output.

[fcb]

24V is above the 2N7002 Vgs(max), it can cope with +/-40V Vgs(max) briefly, but would suggest your application is too much.  Could you replace the jumper with a resistor to lower this?  Are the jumpers field replaceable?

Would suggest that R3/R5 are quite low also.  Depending on the quality of the 10KHz you want you can probably increse these values and lower the current.  Also, the 2N7002 is failry well turned on by 2.5V to 3V, so you could re-ratio your dividers a bit.

Q3 is the biggest issue though.  It is a P-channel and in your circuit it always has some voltage between gate and source. Vgs for this part is -1.5V to -3.5V, so it's probably off at 5V rail (gate will be 4.1V, so Vgs=-0.9V), however at 24V rail it will be at 19.7V (Vgs=-5.3v) so very much ON.

Vgs(max) is also +/-20V, so you might get away with removing R6 - but not a solution I'd be comfortable with.  You are slightly bollox'd if you've done the layout - probably resort to a scalpel to rework it or find a MOSFET that has a bigger Vgs or somesort of protection built in.

Quick other thought - you *might* get away with an N-channel as Q3 if you reverse drain and source, and flip your NPN-PNP assignment, but you won't hit 24V out and may have other complications depending on what you are driving.