Hello,

I am trying to build a simple MOSFET driver that converts a 5V pulse to a 12V pulse. To do this, I used an N-channel (2N7000) and P-channel MOSFET (BSS84), as shown in Fig 1.

If the input signal is a 5V pulse train, I notice that the falling edge of the output pulses decay instead of dropping immediately to GND. Fig 2 shows the signal at point A, and Fig 3 at Vout.

I suspect this has to do with the output capacitance of the P-channel MOSFET creating a low pass filter with the 100k resistor. However, if I change the resistor to 10k, it doesn't seem to affect the output that much. I also tried changing the P-channel MOSFET but the signal shape remained the same.

Could you please advise me how to correct this issue?

Many thanks

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Fig 1 (circuit):

Fig A (point A):

Fig B (Vout):
.

 

Hello,

Is there a load in your circuit?
As shown the output looks open.
Try an 1K resistor on the output and measure again.

Bertus

 

Thanks Bertus - problem solved. Took longer to ask the question here than it did to solve it haha!

 

What does your pulse train look like? And what is its source-sink current capacity?

[never mind, looks like you got it solved]