Author Topic: HV MOSFET vs. HV BJT for Nixie cathode driving  (Read 3490 times)

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Offline shadewindTopic starter

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HV MOSFET vs. HV BJT for Nixie cathode driving
« on: April 24, 2011, 04:24:43 pm »
I designed a little board which uses a 16 output decoder (74HC154) driving a number of MMBTA42 high voltage NPN transistors (that's the SMT version of MPSA42) which drives the cathodes on a Nixie tube. The reason I chose the MMBTA42 is that everyone doing Nixie stuff seems to be using it (or rather the MPSA42, but you get what I mean).

This got me thinking... is there any particular reason why it's better to use this rather than a HV MOSFET? Wouldn't that also eliminate the need for a base/gate resistor or is that needed anyway to limit the current spike when switching? HV MOSFETs have high Rds(on) but I doubt that really matters in this case since it is still very small compared to the anode resistor for the Nixie.

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