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Even faster !

A project log for YGREC-ECL

At the opposite site of the spectrum, this project is incredibly smaller and faster than the relay implementation of YGREC.

Yann Guidon / YGDESYann Guidon / YGDES 01/17/2019 at 21:336 Comments

I found even faster transistors than the BFS480...
The BFP420 is 3x faster, at 25GHz gain-bandwidth product ! This means a gain of 25 at 1GHz, for example.

I received a few hundreds for tests. They are of course more expensive and are packaged alone in a small package (4 pins ??) so the density is lower but it could be helpful for the critical datapath, like the ALU.

I doubt I could measure the frequency of a ring oscillator made with it so I'll have to implement at least 9 stages ! :-P

One important limitation is the operating voltage : 4.5V so this limits the possible topologies.

OTOH it could also be used to build a very good picosecond pulse generator at low voltage :-P

Discussions

matseng wrote 01/18/2019 at 00:13 point

At 11 Eurocents each in 1K qty (Farnell) I wouldn't call them particularly expensive - just a little bit more than double the price of plain old BC547's.

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Yann Guidon / YGDES wrote 01/18/2019 at 00:56 point

BC547 can be sourced as low as .2 to .015€...

https://www.ebay.de/itm/1000-x-BC546B-Si-Transistor-NPN-65V-0-1A-0-5W-TO-92/312004936430 : 14€, or 20€ incl. shipping and taxes.

BFS480 has 2 transistors per package, which is pretty price-effective and dense on the board.

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matseng wrote 01/18/2019 at 08:35 point

Well, you really can't compare prices on eBay with a proper supplier like Farnell. (Which had the prices I quoted). Oranges and apples you know ;-)

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Yann Guidon / YGDES wrote 01/18/2019 at 10:47 point

@matseng in fact... I can ;-) and dollars are dollars ;-)

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Ted Yapo wrote 01/17/2019 at 23:11 point

I wonder what kinds of steps you need to take to discourage parasitic oscillations at some ridiculously high frequency with these things. How would you even know if it were oscillating at 10+ GHz?

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Yann Guidon / YGDES wrote 01/17/2019 at 23:21 point

to prevent resonance, you have to use the https://en.wikipedia.org/wiki/Barkhausen_stability_criterion : add phase or have gain <1 at the unwanted frequencies...

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