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RJM Z-reg + Pass B1

Posted 4th February 2012 at 12:53 AM by rjm
Updated 4th February 2012 at 01:01 AM by rjm

I was asked to suggest a voltage regulator for the First Watt (Pass DIY) B1 buffer. One thing led to another and the next thing I'd sketched up a circuit board for the buffer as well as the regulator.

It's like a B-board, but with the JFET buffer instead of the diamond buffer, and with a single supply and, hence, the coupling caps front and back. Since it's using JFETs for the buffer I used a JFET for the pass device in the regulator, too.

Full credit to Nelson Pass for his design.

Eagle files do not show 2SK170 because the package is not in Eagle. All transistors 2SK170 or equivalent. Zener is 18-22V DO35 or DO41 i.e. Vishay BZX85. V++ is 5-15 V above whatever you select the Zener reference to be.
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Total Comments 4


  1. Old Comment
    Hi great job thank you, can you clarify the voltage with the zener ? I am a bit noob and my English are not so good, so a more detailed explanation would be appreciated.
    Posted 14th May 2013 at 10:28 PM by seakinggr seakinggr is offline
  2. Old Comment
    rjm's Avatar
    As an example, the original circuit specifies +18 V DC power. To obtain this, you would use a 18 or 20 V Zener, and a transformer with 18, 20, 22, or 24 VAC secondary.
    Posted 20th May 2013 at 03:39 AM by rjm rjm is offline
  3. Old Comment
    Posted 18th March 2014 at 12:03 AM by seakinggr seakinggr is offline
    Updated 18th March 2014 at 08:04 PM by seakinggr
  4. Old Comment
    Hi, I tried my own layout in eagle and I think that the TO92 package that is used has the Drain & Source the other way around, can you please confirm?
    Posted 19th March 2014 at 08:24 PM by seakinggr seakinggr is offline
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