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I am trying to convert a 3.3V logic signal to 5V logic signal. I am using a p-channel MOSFET and I can not get it to send the full 5V signal through. Below is the circuit I am using. 3.3V to 5V Converter

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  • \$\begingroup\$ What's the VGS Threshold for your mosfet? \$\endgroup\$
    – Passerby
    May 12 '16 at 20:50
  • \$\begingroup\$ That circuit will require an N-channel MOSFET and will invert your data. \$\endgroup\$
    – Tut
    May 12 '16 at 20:50
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    \$\begingroup\$ We don't know to which component the 5V signal is sent, but if it is some logic IC that has logical levels compatible with TTL, you may ba able to send the 3.3V signal directly to it. Standard 5V and 3.3V logic levels are compatible. Check the Voh voltage of the 3.3V device against the Vih voltage of the target 5V device. \$\endgroup\$
    – dim
    May 12 '16 at 21:02
  • \$\begingroup\$ @dim only if it's 0.6 * VCC. Most ICS I've seen are 0.7 * VCC, or 3.5V minimum. \$\endgroup\$
    – Passerby
    May 12 '16 at 21:16
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Use an N-channel MOSFET, or swap the 100k resistor and the P-channel MOSFET.

Also, it'll work a bit better with a lower value resistor. Say, 10k. And both circuits will invert your logic. If you cannot deal with that, then you need a few more components (another MOSFET, for instance).

See the below diagram for two ways that work.

schematic

simulate this circuit – Schematic created using CircuitLab

The MOSFETs in the schematic are merely symbolic, the part numbers may or may not be appropriate.

Because of your 3.3V input, you must choose a MOSFET with an appropriate low turn on voltage. That is, \$V_{gs(th)}\$ must be sufficiently below 3.3V, otherwise your MOSFET will not turn on or be barely on.

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  • \$\begingroup\$ There are many MOSFETs now in which your P solution will not close enough to create a 0V out with 3.3V in. However, connect them in series and you have a nice example of your second suggestion ^.^ \$\endgroup\$
    – Asmyldof
    May 12 '16 at 21:04

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