Can RF transistor junction be used as a diode?

[Sinedup]

It it possible to use some ancient vintage NPN germanium transistors' base/emitter as a 2-lead germanium diode?
What about the higher-frequency BFY90?
I have been given a "scrap" box full of old OC76 and (OC90?).
Simply for experimentation in RF filters & tanks.

 

[JimB]

It it possible to use some ancient vintage NPN germanium transistors' base/emitter as a 2-lead germanium diode?

Probably, but they will probably be poor performers.

What about the higher-frequency BFY90?

Probably better to use as a transistor and buy some real diodes.

I have been given a "scrap" box full of old OC76 and (OC90?).

OC76 is PNP not NPN.
Never heard of an OC90 though.
The cynic in me says that being given a box full of old germanium transistors is like winning third prize in a beauty contest.

Simply for experimentation in RF filters & tanks.

How will this lot help in experimenting with filters and tanks (tuned circuits ?).

JimB

 

[Mikebits]

How will this lot help in experimenting with filters and tanks (tuned circuits ?).

Maybe he is thinking of using the device as a tuning diode?
I came across an article that discusses such a thing.

https://www.google.com/url?sa=t&rct...aSpTmca7g&sig2=z9qJvnYqVdELh_1D9zsTAw&cad=rja

 

[ci139]

found from web about https://wiki.analog.com/university/courses/electronics/electronics-lab-3

basically if you have a proper diode for intended operation you don't need transistor substitutes

for some very specific situation you may have to combine different diodes in series / reverse /parallel ... with transistor substitutes either using BE , CE (with 3-rd electrode not connected) or EC-B or CB-E or BE-C

for example : for a simulation -- i found -- the weak signal driven bjt booster-comepensation(/opener-(junction-discharger)) diode (a reverse from E to B) to be a diode from the very same transistor in B-EC configuration e.g. Si-NPN as P-NN (E & C shorted together)

PS! most likely the transistor-diodes have much larger **broken link removed** (depends on I.FW) and series resistance than "conventional" diodes but they may provide lower voltage drop , higher power e.c. as fuzzily hinted above

 

[RichTheDude]

Probably, but they will probably be poor performers.

OC76 is PNP not NPN.
Never heard of an OC90 though.
The cynic in me says that being given a box full of old germanium transistors is like winning third prize in a beauty contest.


How will this lot help in experimenting with filters and tanks (tuned circuits ?).

JimB

To the OP and Jim, try looking at the prices of OC76s etc on eBay. Sell your box on a piece by piece basis for megabucks and buy some modern diodes, transistors and other electronics gear with the proceeds.

 

[JimB]

To the OP and Jim, try looking at the prices of OC76s etc on eBay.

OK, the cynic in me says sell them on eBay and buy some decent stuff!

JimB

PS, anybody want to buy some 2N404s ?

 

[ci139]

i have used pnp Ge-s for 1 battery oscillators + line audio amps + positive current sorce ...
... random usage

random 2