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General => Open Discussion => Topic started by: Matt on February 19, 2016, 08:08:09 PM

Title: Transistor hfe doubler?
Post by: Matt on February 19, 2016, 08:08:09 PM
Does this really work?

http://s.webry.info/sp/houshu.at.webry.info/200604/article_6.html
Title: Re: Transistor hfe doubler?
Post by: zombie_rock123 on February 19, 2016, 08:36:01 PM
Never seen that before, but very interesting. I usually go for Darlington pairs where I need the higher HFEs and all I have to hand is low gain Ge. Definitely worth a breadboard!
Title: Re: Transistor hfe doubler?
Post by: culturejam on February 19, 2016, 08:37:51 PM
I think it should work. But usually, increasing hFE also increases leakage (and usually also noise floor).

I did some testing with very low gain Ge trannies (like 10 - 30) in darlington pairs, and while it did work, it sounded like garbage because of the amplified leakage.
Title: Re: Transistor hfe doubler?
Post by: zombie_rock123 on February 19, 2016, 09:31:01 PM
Culturejam, were your darlingtons using Russian transistors? Ive always had great results with them but now I want to revisit and make sure I wasnt hearing things :-\
Title: Re: Transistor hfe doubler?
Post by: kgull on February 19, 2016, 09:40:19 PM
A Sziklai pair (https://www.wikiwand.com/en/Sziklai_pair) is another interesting topology if you're looking to experiment :D
(https://upload.wikimedia.org/wikipedia/commons/thumb/6/64/Compound_trans.svg/320px-Compound_trans.svg.png)
Title: Re: Transistor hfe doubler?
Post by: culturejam on February 19, 2016, 10:13:13 PM
Yeah, Sziklai pair works about the same. The classic model has a 1K-ish resistor from collector to base of the PNP to stabilize things, but it works without it as well. At least for fuzz circuits.
Title: Re: Transistor hfe doubler?
Post by: Matt on February 19, 2016, 10:29:12 PM
Lots to try out for sure. Thanks for the input. I have some Russian ge s laying around.
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