Fastest Germanium ?

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How fast can germanium transistors compute ? And how much current will that draw ?

Yann Guidon / YGDESYann Guidon / YGDES 11/07/2016 at 21:083 Comments

How fast can germanium transistors compute ?

This question might receive an answer soon.

While visiting one of the few remaining electronics parts stores of Paris, I found that they have a little stock of Ge. And I got their last AF280. From the datasheets:

This transistor is particularly intended for use in mixer and oscillator circuits up to 900 MHz in diode tuned tuners.

So the intuition worked (higher number means better performance, right ?), this transistor is faster than the 500MHz AF240 (though only by 10% because its transition frequency is actually rated for 550MHz) and the datasheet claims a power gain of 16dB @800MHz (power gain of approx 40, or amplitudes 12 ?) to a 2K ohms load (compatible with an ECL gate impedance). Too bad my DDS can't go so fast, but I'll try to hack a picosecond pulse generator...

I got 13 AF280 and if I don't make mistakes, I might be able to build two NOR2 or NOR3 gates. Enough to test some logic and/or a flilp-flop :-)

It just appears now that the answer I might get is not of the kind I expected intially.

With such fast transistors, my lab tools are already too slow. I consider building a picosecond pulse generator but that won't help much.

Furthermore, if I build a globule that is clocked so fast, I have another problem : memories. Latency and bandwidth will be hard to match with the expected means and I'll have to resort to using fast silicon chips.

20170106: I found a batch of AF439, roughly equivalent to the AF280/279, so I might be able to build more than a couple of gates :-)

It's going to be fun, though, since the hFE is ">10" ( The frequency is rated at 400 and 800MHz depending on the sources, but this speed will be held back by poor amplification.


Yann Guidon / YGDES wrote 05/24/2020 at 03:06 point

Note for later : ok my tools are too slow for the fastest of the fastest of the germaniums... but my experience with the 2N2369 shows the solution : make a ring oscillator ! see Beyond 2ns with 2N2369A

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add_ocean wrote 09/25/2017 at 23:26 point

Looking into russian transistor selection book, there are types with transition frequency from far above 1 and up to 4,8 GHz. Though those types are from rare to almost unobtainable. But even ГТ313В on sale at ebay can be up to 1GHz according to datasheet.

I could advise on soviet germaniums, it's not so difficult to get best from ebay (high gain etc.), just one needs to pay close attention to letters. Like, do not take МП13Б, go for МП16Б or МП42Б instead.

PS: i would be happy to see your germanium projects progressed, just like the idea and approach. Do not know if they are posponed or abandoned for now, or you still working on.

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Yann Guidon / YGDES wrote 09/25/2017 at 23:53 point

They are postponed so far, because I focus now on the relay-based hexadecimal display. Yes I need user-friendly ways to display informations ;-)
After the relay version, I'll try to do one with KT315 and then fuse PROMs...

Those are not high-speed circuits however (so they can even use crappy МП13)  but I'm just starting, and trying to assemble a processor (at this moment the #YGREC8 ). Display would need to be at least 8 number for PC, 1 number of result bus, 1 number for current instruction... That's at least 6 hex digits for the 8-bits version :-) and some more for the registers...

So yes, at this moment I'm in "ridiculously slow electronics" domain. Do I look like I have a short attention sp

Oh look what I found on eBay ! :-P

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