Unsing a PNP Vbe multiplier to replace a germanium diode

Thread Starter

omers

Joined Dec 5, 2017
4
I have the intention to replace a germanium diode with a PNP germanium diode in an old amplifier circuit How do I determine the correct R1 and R2 on a 1K trimpot if i chose another germanium transistor with a different voltage drop at Vbe on the circuit displayed?
 

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Sensacell

Joined Jun 19, 2012
2,852
This will make a pretty crappy diode, looking like a 1K resistor when reverse biased?

What does this diode circuit accomplish in the actual circuit?
 

Thread Starter

omers

Joined Dec 5, 2017
4
It will be used to replace a 1N2326 diode in an old Fisher receiver The Vbe of the Russian germanium transistor, MP20 is around 0.120 at 2mA
 

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DickCappels

Joined Aug 21, 2008
7,564
It will not work. The like a shunt regulator that can be set anywhere between 1 Si diode drop (about 0.6V) up to the Collector-Emitter breakdown voltage. It cannot give the same forward drop as a germanium diode.

Try a silicon Schottky diode -it will have about the same forward drop as a germanium diode.
 

Thread Starter

omers

Joined Dec 5, 2017
4
This is a germanium transistor Putting the collector and base together as the cathode, and the emitter as the anode , give a reading of 0.120 mV @ 2 Ma

Isn't the circuit , called a, "rubber diode"?
 

DickCappels

Joined Aug 21, 2008
7,564
Then don't bother with the pot. Just connect the bast to the collector -that gives you a very nice germanium diode, unless you need to have it adjustable for some reason...
 
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