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PeterJ
PeterJ
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I want to use a pair of N and P channel mosfets in a totem pole arragement to shift a VFD display on and off using a 74LS247 decoder/driver. I would put the P channel with the source pin on the top and connected to the 25 volts the VFD requires.The The P channel drain pin would be connected N channel drain pin. The junction of both drains would be my output (25 Volts). The source pin of the N channel would be connected to ground.

The gates of both the P and N channel mosfets would be tied together and powered from the "Open Collector" output of the 74LS247 decoder/driver to turn on and off the appropriate mosfet. I plan on using a Fairchild FDS8958AFairchild FDS8958A mosfet complementary pair. You can Google the part number for the complete datasheet.

QuestionQuestions: a.) do I need a series resistor in series with the LS247 output and the two gates? b.) What value do I need? c8.) do I need pullup / pulldown resistors between the source pin and gate pins?

  • Do I need a series resistor in series with the LS247 output and the two gates?

  • What value do I need?

  • Do I need pullup / pulldown resistors between the source pin and gate pins?

I want to use a pair of N and P channel mosfets in a totem pole arragement to shift a VFD display on and off using a 74LS247 decoder/driver. I would put the P channel with the source pin on the top and connected to the 25 volts the VFD requires.The P channel drain pin would be connected N channel drain pin. The junction of both drains would be my output (25 Volts). The source pin of the N channel would be connected to ground.

The gates of both the P and N channel mosfets would be tied together and powered from the "Open Collector" output of the 74LS247 decoder/driver to turn on and off the appropriate mosfet. I plan on using a Fairchild FDS8958A mosfet complementary pair. You can Google the part number for the complete datasheet.

Question: a.) do I need a series resistor in series with the LS247 output and the two gates? b.) What value do I need? c8.) do I need pullup / pulldown resistors between the source pin and gate pins?

I want to use a pair of N and P channel mosfets in a totem pole arragement to shift a VFD display on and off using a 74LS247 decoder/driver. I would put the P channel with the source pin on the top and connected to the 25 volts the VFD requires. The P channel drain pin would be connected N channel drain pin. The junction of both drains would be my output (25 Volts). The source pin of the N channel would be connected to ground.

The gates of both the P and N channel mosfets would be tied together and powered from the "Open Collector" output of the 74LS247 decoder/driver to turn on and off the appropriate mosfet. I plan on using a Fairchild FDS8958A mosfet complementary pair.

Questions:

  • Do I need a series resistor in series with the LS247 output and the two gates?

  • What value do I need?

  • Do I need pullup / pulldown resistors between the source pin and gate pins?

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Ed Edmondson
Ed Edmondson
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Using MOSFETS for a Level Shifter

I want to use a pair of N and P channel mosfets in a totem pole arragement to shift a VFD display on and off using a 74LS247 decoder/driver. I would put the P channel with the source pin on the top and connected to the 25 volts the VFD requires.The P channel drain pin would be connected N channel drain pin. The junction of both drains would be my output (25 Volts). The source pin of the N channel would be connected to ground.

The gates of both the P and N channel mosfets would be tied together and powered from the "Open Collector" output of the 74LS247 decoder/driver to turn on and off the appropriate mosfet. I plan on using a Fairchild FDS8958A mosfet complementary pair. You can Google the part number for the complete datasheet.

Question: a.) do I need a series resistor in series with the LS247 output and the two gates? b.) What value do I need? c8.) do I need pullup / pulldown resistors between the source pin and gate pins?