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Germanium Diodes

10/15/2000 4:25 PM
Germanium Diodes
I recently tried to stock up on 1N34a's and 1N60's at Mouser and found they are no longer stocking these devices. They had an alternate part listed. I wrote the staff and asked if it was a germanium diode and they said it was silicon. Does anyone still make germanium devices(diodes, transistors), or are we living on NOS? Is there any way to measure a diode to tell if it's germanium or not? I wound up ordering them from the Shack. The 1N60's looked the same, but the 1N34A's had a green cathode band and the glass to metal seal was longer and bright red. Do I really have 1N34A's?  
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10/15/2000 4:53 PM
Joe Fuzz

Bill: If you've got a breadboard, you can check the forward-biased voltage drop on your diodes.  
Try wiring a 9V battery across a 470 ohm resistor and your diode in series. The diode's cathode (the side with the band) should connect to the negative side of the battery. The diode's anode (the side without the band) should connect to one side of the 470 ohm resistor. The other side of the 470 ohm resistor should connect to the positive side of the battery.  
Once you've got this set up, measure the voltage across the diode. Germaniums will be between .2V and .3V. Silicon will be between .6V and .7V.  
(Note: if you try this series arrangement and get 9V across the diode, you put it in backwards. No biggie. Remove the power and turn the diode around. Reapply power and measure again.)
10/15/2000 5:57 PM

Thanks Joe
10/20/2000 3:59 PM

I tested the Diodes as you suggested Joe, but I got 1.7V for the 1N34A's and 2.1V for the 1N60's. I measured some silicons and they were right were you said they'd be. I pulled out some old 1N34A's that were blue and clearly marked 1N34A and they tested .3 to .34V as you said they should. Can anyone tell me what the heck they sold me?
10/20/2000 6:45 PM

The only devices I have seen with that high voltage drop are LEDs.  
1.7 to 2.1 is very high - but if you measured them correctly, this is very cool!  
I've been looking for single diodes with this high voltage drop.
10/20/2000 10:20 PM

For what type of application Aron? I have 20 of each. Will they work in the usual Ge diode applications? Softer distortion than Silicon? If not, I know where you can get some really cheap. :-)  
10/20/2000 10:24 PM

These would be great for feedback loop clippers - when you want more dynamic range in the op amp section. Not necessarily softer distortion - just less distortion and more headroom.  
What diodes are these again??? Number???

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