Good replacement part for 2SD401A?

Discussion in 'General Electronics Chat' started by Razor Concepts, Aug 28, 2013.

  1. Razor Concepts

    Thread Starter Active Member

    Oct 7, 2008
    Hi, I'm trying to build this TENS circuit here:

    It calls for a 2SD401A PNP transistor.

    Can I just replace it with a generic, high voltage NPN transistor? I believe the TENS circuit simply switches high voltage (80-100v) at around 300hz. I think the speed is fine for modern transistors, so all I need to do is find one that can handle the voltage?
    Last edited: Aug 28, 2013
  2. wayneh


    Sep 9, 2010
    And current. I agree that if you find something with similar voltage and current ratings it should be fine. Note you need a PNP, not NPN.

    FWIW, I made my TENS unit by switching low voltage and then stepping it up with a transformer taken from an old wall wart.
  3. PackratKing

    Well-Known Member

    Jul 13, 2008
    Your number jives with an EGC 375, an npn Si. vertical deflection, freq. of 8 Mhz BVcbo 200v in a TO220 package...
  4. ian field

    Distinguished Member

    Oct 27, 2012
    My databook has that listed as NPN; 2A 200V 20W 10MHz. It lists comparable types; BD239F, 2SC2660, 2SD610, 2SD1138.
  5. ian field

    Distinguished Member

    Oct 27, 2012
    I was just thinking you might do better with the MOSFET from the primary side of a small appliance SMPSU, when I looked at the schematic you posted, and noticed the intensity pot & resistor looks a bit unlikely - you might be better off varying the pulse width. I did a quick search for "CMOS PWM">
  6. Willen


    Nov 13, 2015
    The thread is little old though-- thread starter is showing a circuit from and the site author is Gary Lecomte. The transistor is 2SD401A (2A, 150V and 25W) EXACTLY because today I got some parts from him and I got 7 pieces of 2SD401A NPN. They are NPN, I tested, however all the information I wrote here, has been already notified in the schematic of the TENS there. Any high voltage transistor like 13003 (available inside CFL bulbs or cell phone wallwart supply) could do the job.
    Last edited: Feb 26, 2016
  7. Dodgydave

    Distinguished Member

    Jun 22, 2012