Lower Gain Si PNP Transistors

[YouAre]

Hey Guys,

I found a project that calls for ac128 PNP Ge transistors. Since they're not available anywhere, Steve at Small Bear and others have shown me alternative PNP Ge's that I could use. But I was wondering of any Si substitutes. Are there any PNP Si transistors that have an Hfe gain range of 70-120ish? Thanks for the help!

[mac]

mmhh... KSP92, 2N3905, BD140

mac

[YouAre]

Thanks! I could only find the bd140 at digikey. Everything else was neither available at smallbear or digikey. I'm not making a mouser order anytime soon, so I didn't check there.

Great avatar by the way!

[brett]

Hi
the BD140 ranges around hFE=150.
the TIP32B is more like 100 (TIP32A being lower by 20% and TIP32C higher by 20%).
cheers

[YouAre]

Wow! Thanks!

[mac]

First, remember that si and ge have different Vbe and that ge leaks. You might need to adjust transistor bias.
Second, you can convert the circuit to NPN, and use 2N2369A.

IMHO BDxxx transistors do not sound good.

mac

[Solidhex]

Don't forget 2n2904/2905's. The 2N2904's can dip down into the too low range (40hfe) but don't go higher than 100hfe usually. The 2N2905's can get up to 300hfe but its usually easy to find a Fuzz Face pair with them.

--Brad

[smallbearelec]

If you want to do a silicon Fuzz Face, go NPN. You will wind up with a pedal that will not require a separate power supply and can sound really excellent. This article:

http://www.smallbearelec.com/HowTos/BreadboardSiFF/BreadboardSiFF.htm

Contains a bunch of ideas and tweaks. The 2N2369A that someone mentioned makes a very good Q1.

Regards
SD

[YouAre]

First, remember that si and ge have different Vbe and that ge leaks. You might need to adjust transistor bias.
Second, you can convert the circuit to NPN, and use 2N2369A.

IMHO BDxxx transistors do not sound good.

mac

If you want to do a silicon Fuzz Face, go NPN. You will wind up with a pedal that will not require a separate power supply and can sound really excellent. This article:

http://www.smallbearelec.com/HowTos/BreadboardSiFF/BreadboardSiFF.htm

Contains a bunch of ideas and tweaks. The 2N2369A that someone mentioned makes a very good Q1.

Regards
SD

Thanks for the advice guys, but it's not a Fuzz Face. It's not a classic type fuzz, so the circuit does have a negative ground. Thanks for looking out for me!

[Gus]

Posts about using med power transistors go back a few years at this site and Ampage IIRC.

Dies size >miller, possible lower noise, lower gain, more "bent" hfe vs Ic at lower Ic.