An old "500MC biquinary counter"

Could they be Shockley diodes? Those are similar to SCRs but without a gate connection and can only be triggered via avalanche breakdown or dv/dt.

Well, it does say "500MC biquinary counter". ;)

I suspect it was never an actual IC.

Cheers

Phil Hobbs

But even the fastest ones have crazy amounts of capacitance because they're still huge and the depletion zone is so thin because of the ridiculously high doping.

I have some Russian GaAs ones on my desk that I'll have to try out. They're in a beam-lead package. (It's like 2 inches worth of beam lead, but flat, so they must be fast). ;)

Cheers

Phil Hobbs

Cheers

Phil Hobbs

Maybe tunnel diodes forming the storage latches.

Cheers

Phil Hobbs

Tunnel diodes.

AFAIU this is an IC. Has there been a process that could integrate those?

Not that I know of. TDs were hand-welded and etched, a truly bizarre fab process.

The only photolithographically-formed germanium devices that I've heard of are back diodes, essentially TDs with very low peak point current, still used as RF detector and mixer diodes.

I still have a bunch of TDs. Haltek had a bin full and didn't know what they were, so I got them for 10 cents each.

Yeah could be Shockley diodes (aka 4-layer diodes) but last time I saw one in a schematic the symbol was different. However they are not hi-speed parts and even in their heyday would not have seen use at 00s of kilohertz let alone megahertz.

Diac is a still-available kindof breakover diode but higher voltage and bidirectional. 4-layer diodes I saw were made with breakover voltages from 8 to 22V and 5-10% tolerance. TC was remarkable good and they made good semi-precise timers (but not for nano-seconds). Diacs typically breakover 28-35V and are not tightly specified.

Another option is that is just an old symbol for a zener diode?

But for those speeds I reckon they must be tunnel diodes. That would tie in with the emitter coupled logic and 10mA tail current. Tunnel diodes are fast. Due to the very high doping some older ones have now diffused themselves into mush.

piglet

Maybe in GaAs, but not Ge, I'm pretty sure. Besides leakage, Ge isn't suitable for normal planar processing--its oxide is only slightly better than carbon's. ;)

Cheers

Phil Hobbs

Nice. I got a bunch off eBay, but they're only 10 mA peak current so they're not that fast. The quick ones are the 200 mA types.

Cheers

Phil Hobbs

Schematic symbols in the olden days were often weird. Take a look at the potmeter representations here (9th and 10th left from the top):

That IC could be from an era where a few hundred kHz was considered blazingly fast. Shockley diodes would offer the nice advantage of introducing hysteresis which improves the noise robustness of this counter.

With tunnel diodes I wouldn't know who they'd integrate those onto a chip.

I also think they're zeners.

The sideways schematic presentation obscures the Schmitt operation.

I suspect the zeners are for level shifting. ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

Thinking outside the box... producing elegant solutions.

Yeah, mine are 5 or maybe 10 mA, nanosecond rise times. The high current stripline parts from RCA and GE got down to 25 ps rise times, in maybe 1963. I have the 1963 RCA Tunnel Diode Manual!

Basically, you etch away Ge and make the diode tinier and tinier, until you can't any more.

With 2k resistors and stuff in there it would never even get into the VHF range :-)

Looks like they're using them as a "solid-state neon lamp"

Looks like the circuit is a chain of a variation on this with whatever that thing is replacing R1:

On Saturday, February 11, 2017 at 7:33:02 AM UTC+11, snipped-for-privacy@gmail.com wrot e:

table for normal planar processing--its oxide is only slightly better than carbon's. ;)

GeO2 may not insulate as well as SiO2, but it's less volatile than CO2 - it

As a greenhouse gas, it's not going to be a problem for a few billion years .

The RCA 40079 had Ip of 200 amps, Cj = 1.25 uF, Rj = 1 mohm, Tr = 4 ns, 1" diameter stud package.

TDs were fun.

Do Russians still make TDs?