Low Gain Silicon Transistors

From my stash:
MPS6530 measured HFE = 75 @ Ic = 5.8mA
2N4123 measured HFE = 59 @ Ic = 5.9mA
2N6517 measured HFE = 73 @ Ic = 0.68mA

Mouser has 2N6517 for 0.183 ea in tens and 0.117 ea in 100s.
2N3903 are also a good choice.

For any part number, there is a range of HFEs. Get more than you need and cherry-pick them. NB: if you buy them from an authorized distributor like Mouser or DigiKey, chances are that all of the ones you'll get come from the same wafer lot and as such will be very consistent.

Don't be afraid to buy BJTs from Amazon, eBay or even AliExpress. Just test 'em and demand a refund if they're out of spec.

It's funny how most people pay a premium for high-gain transistors and here we are, scrounging for the low-gain ones. Sometimes we have to pay a fucking premium for them!
 
Ginsly said:
I'm not sure how low you need em, but the recent 2N3903s from Mouser hover around 115hFE on a DCA55.
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dank 🤙 ive got x10 of these already from a previous order, but thought I might grab some more, or something else to try while im doing an order
Ginsly said:
Where are you located? From my end 10 of them brings em down to about 41 cents.
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a land where a dollar isn't worth much
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Chuck D. Bones said:
Mouser has 2N6517 for 0.183 ea in tens and 0.117 ea in 100s.
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oh hell yeah, these are a great price! will give them a go.
 
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I recently discovered a couple of boxes of BD139/140s in my stash (that I was given years ago and didn't realize were particularly useful).

I've tested around 20 of each out of a couple of hundred, and about 25% are 65-85 hfe.

Guess I'm doing some silicon fuzzes 😅
 
drew.spriggs said:
I recently discovered a couple of boxes of BD139/140s in my stash (that I was given years ago and didn't realize were particularly useful).

I've tested around 20 of each out of a couple of hundred, and about 25% are 65-85 hfe.

Guess I'm doing some silicon fuzzes 😅
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Power transistors in general seem to be lower gain, just mind the pinout and the package size. I found some of them also have higher parasitic capacitances than regular transistors, which may or may not matter and may or may not be a good thing as it can lead to high-end roll-off due to the miller effect limiting the gain at higher frequencies.
 
lowpitch said:
Power transistors in general seem to be lower gain, just mind the pinout and the package size. I found some of them also have higher parasitic capacitances than regular transistors, which may or may not matter and may or may not be a good thing as it can lead to high-end roll-off due to the miller effect limiting the gain at higher frequencies.
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I’ve personally built dozens of fuzz circuits with that combo. They come highly recommended.

Some history; a couple decades ago myself and a few others on that forum were experimenting with that piggybacking technique mentioned earlier trying to get a low gain silicon solution when (I believe it was) Brett came across those and posted his findings. As a result the piggybacking idea was pretty much abandoned in favor of those because that combo sounded soooooo good.
 
jessenator said:
Another solution, if quite clunky space-wise, is to piggyback transistors to get lower gain. I haven't messed with it much, so more experienced folks can chime in. I'm not sure if it's a perfect 50% of the original gain, but it definitely gets you lower. It's meant to "emulate" a germanium transistor for NPN fuzz faces, IIRC.

Again, experienced ones, correct me here…

View attachment 70624

I made a micro pcb for this, but never had it fabbed.
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Is this what the new PedalPCB Silica Fuzz is doing?
 
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