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This question already has an answer here:

I made 2 PCB, one is a logic driver with NAND Schmitt trigger (74HC132D & CD40106B) to drive FORWARD and BACKWARD of H-bridge channel, the other board is the H-bridge Power MOSFET, which used 4 P & 4 N type MOSFET (paralleled), I might add P type MOSFET drived by pull-push circuit for enhance fast switching, following is the schematic and its images

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NAND shield alone, work fine with Arduino and put the FORWARD and BACKWARD pins of MOSFET shield in opposite logic level (5 volt), but when I attached the MOSFET shield, that logic level drop to 2 volt, it seems input impedance of CD40106B inverters is so low to drive MOSFET gate and thus MOSFET didn't turn on, then I increased the MOSFET pull down gate resistor form 1k to 3.6K but it burn my MOSFET, it seems slightly change in logic level voltage from 2 to 2.4 put the MOSFET in conduct mode with high Rds, I did some voltage measurement by multimeter (red number in schematic image) that shows Vgs not enough for conducting the MOSFET. My question is how to find a responsible component for droping the logic level voltage?

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marked as duplicate by Elliot Alderson, Dave Tweed Sep 20 '18 at 14:40

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  • \$\begingroup\$ ”it seems input impedance of CD40106B inverters is so low to drive MOSFET” Please show oscilloscope measurements! ”logic level voltage from 2 to 2.4” Is that in volt? What rise rate do you expect out of Q6-R18? \$\endgroup\$ – winny Sep 20 '18 at 14:08
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    \$\begingroup\$ Also possibly a copy of electronics.stackexchange.com/questions/395829/… \$\endgroup\$ – Elliot Alderson Sep 20 '18 at 14:40
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    \$\begingroup\$ If you have additional information related to your original question, use the "edit" button to add the information there. Do not create a duplicate question. \$\endgroup\$ – Dave Tweed Sep 20 '18 at 14:42
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    \$\begingroup\$ You got a lot of good advice in the comments, which you seemed to be ignoring. It's no wonder people quickly lost interest. In any case, creating duplicate questions is not the way to get attention. It just annoys the other site users. \$\endgroup\$ – Dave Tweed Sep 20 '18 at 15:38
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    \$\begingroup\$ @Hamidsk A comment was made on one of your other posts about mis-wiring of your Forward and Reverse control signals. You replied to that comment that they were not. Are you really sure? (Hint : Make another very close comparison of the two schematics.) \$\endgroup\$ – Tyler Sep 20 '18 at 17:47