Author Topic: Germanium diode forward voltage drop  (Read 8380 times)

nieradka

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Germanium diode forward voltage drop
« on: March 20, 2013, 01:51:32 PM »

Is there a way to determine the forward voltage drop of a germanium diode from a datasheet? All of them seem to state that the forward voltage drop is 1v which cant be right. Im running low on OA126 diodes which I love as clipping diodes, but they seem to have disappeared from ebay, so I was trying to see if there is an equivalent, in the russian D9 series, or other commonly ebay-able and cheapish diodes, and dont really want to order 10 different diodes just to get 10 functionally identical for clipping diodes.



RobA

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Re: Germanium diode forward voltage drop
« Reply #1 on: March 20, 2013, 03:06:54 PM »
The data sheets typically just give min, max, and typical values and for the Ge's usually not even all of those. My experience with Ge diodes is that they are all over the place as far as the forward voltage drop. I mean that within one type of Ge diode that forward voltages vary widely.

Also, I think there is a lot more to it than the forward voltage as far as the clipping of the Ge diodes. I've matched forward voltage drops of 1N100, 1N34a, and 1N270's to each other and put them in the same breadboarded Distortion+ circuit and they sound different.
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midwayfair

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Re: Germanium diode forward voltage drop
« Reply #2 on: March 20, 2013, 04:16:17 PM »
Im running low on OA126 diodes which I love as clipping diodes, but they seem to have disappeared from ebay, so I was trying to see if there is an equivalent

There is no equivalent. All other germanium diodes will clip at about half the forward voltage. Silicon diodes with the same Fv don't sound the same.

Damn it. I should have bought more before I started posting everywhere about how good they were.
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hammerheadmusicman

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Re: Germanium diode forward voltage drop
« Reply #3 on: March 20, 2013, 05:26:08 PM »
i bought some from chromosphere, and found them on ebay incase i liked them, which i DO!

However the listing has dissapeared, but, i 'watched the item' so i have the users name in my watch list..

http://www.ebay.co.uk/usr/pedalhacker


worth a message, i bet he still has a load, he was selling them by the 50..

George
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nieradka

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Re: Germanium diode forward voltage drop
« Reply #4 on: March 20, 2013, 05:53:22 PM »
I find it hard to believe there is nothing close, I have some d9 series (L? I cant remember) that all test around .45 which is higher than the usual ge diode.  But i cant find a datasheet for the oa126, or figure out what values on a datasheet I could compare if I had one, and would rather not poke and hope.

RobA

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Re: Germanium diode forward voltage drop
« Reply #5 on: March 20, 2013, 11:18:44 PM »
What's the forward voltage range on these?

If you want the sound of Ge but a higher forward voltage, you can always double them. I've done that with a couple of pedals to get the output level to match when flipping the diode switch.
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billstein

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Re: Germanium diode forward voltage drop
« Reply #6 on: March 20, 2013, 11:59:56 PM »
What's the forward voltage range on these?

If you want the sound of Ge but a higher forward voltage, you can always double them. I've done that with a couple of pedals to get the output level to match when flipping the diode switch.

By doubling. Is that in series or parallel?

RobA

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Re: Germanium diode forward voltage drop
« Reply #7 on: March 21, 2013, 12:19:44 AM »
In series. The way you wire two together for one half of an asymmetric clipping setup.
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midwayfair

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Re: Germanium diode forward voltage drop
« Reply #8 on: March 21, 2013, 08:32:50 AM »
I find it hard to believe there is nothing close, I have some d9 series (L? I cant remember) that all test around .45 which is higher than the usual ge diode.

OA126 clips at ~.65v.

Okay, I lied, there are some other "close" diodes, but they're not exactly common: OA128 I know is one, probably a couple other things with really close part numbers.
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ichilton

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Re: Germanium diode forward voltage drop
« Reply #9 on: April 14, 2013, 02:00:19 PM »
Did anyone find a source of OA126's?

Thanks,

Ian

hammerheadmusicman

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Re: Germanium diode forward voltage drop
« Reply #10 on: April 14, 2013, 03:25:24 PM »
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=390571507460

This guy had lots of 50, but he only seems to have 10's on there now..

George
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ichilton

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Re: Germanium diode forward voltage drop
« Reply #11 on: April 14, 2013, 03:50:17 PM »
Ah, cool - thanks.

How much we're the 50's when he was selling them?

Do you know if he ships to the uk and how much? - looks like he didn't show when I searched as he isn't showing he does.

Thanks,

Ian