Low voltage negative resistance oscillator design, lessons learned

You can build an okay oscillator using piglet/Win Hill's topology from the AoE x-chapters, I got an LC working down to about 1.8 volts with that one with a fairly low Q coil using the negative R to cancel it. a wide tuning range is impossible though because the slope of the negative resistance changes with load and there's not enough headroom to easily buffer it to isolate it from the tank, there's almost always too much gain or too little and...bla bla bla world of pain, larry.

On a sunny day (Thu, 8 Aug 2019 03:24:11 -0400) it happened bitrex wrote in :

You did not try a tunnel diode?

I don't think I've ever even _seen_ a tunnel diode in the real world, much less used one for anything! aren't they usually used for microwave frequency oscillators and such? I'm not going that fast.

On a sunny day (Thu, 8 Aug 2019 12:52:35 -0400) it happened bitrex wrote in :

Few MHz works OK too, were used in the FM modulator of some Ampex quadruplex video recorders, say 5 MHz to 7 MHz sweep or there about.

ebay has plenty:

AFAIK the frequency low side does not have a limit.

Not sure that will work in your circuit, what exactly are you trying to accomplish with that circuit?

The trigger circuit in Tek 4x5 era scopes was famously good. My

350MHz Tek 485 reliably triggers on a 1.1GHz signal. I suspect it would go higher, but the amplitude is then only 0.2 divisions.

Step generators, of course; 50ps or less 0.4V into 50ohms is achievable.

Increasing the Q factor of a pathologically low-Q coil, like a Q of say

2 at 3 MHz, so you can build a tank-type oscillator from it at a lower frequency than up where the L has a good Q which might be 50 or 100MHz. at low voltage, say 2 volts.

A cheap AD8515 works down to 1.8 volts and with 3 resistors in the negative-resistance configuration, even at 2 v it has enough oomph and bandwidth to make even a crap L ring nicely in a tank circuit like:

On a sunny day (Thu, 8 Aug 2019 14:26:44 -0400) it happened bitrex wrote in :

OK, got the idea. If you look at the wikiedia link I gave, enlarge the picture of the Tek trace

then you see the middle of the negative resistance area is around 325 mV for a Ge tunnel diode, ebay has those too it seems:

But if your solution works for you OK.

Forgot a link:

Unfortunately negative resistors don't have imaginary noise. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

well clearly you just need to couple them to a "negative heater" and cool them down!

Sorry, I mean un-heat them.

Ah, like the solar-powered flashlight!

On a sunny day (Thu, 8 Aug 2019 16:39:41 -0400) it happened bitrex wrote in :

I stil wonder, from the room temperature super conductor postings recently if one can use ultrasound to slow the motion of atoms in a crystal down like we use laser cooling to do it with a gas. I want a Usenet patent for that,

I should try it and measure it but am no physicists, limited lab space and equipment, lame excuse I know.

so then a resistor element with piezo cooler... noise reduction, probably gives you the piezo signal hey, maybe we can filter that out, oh wait LOL

A properly designed JFET-based oscillator can go as low as 25mv of supply voltage. A random one should have no problems at 0.5V, BTDT.

Best reards, Piotr

Give them a bulky tank circuit and they will go as low as 1MHz. But what are you tryig to achieve?

Best regards, Piotr

I wonder if there is a loose analogy between the evanescent component of an EM field that allows you to break the Abbe resolution limit and something resulting from a specifically designed material structure that would allow you to go well below the classic Boltzmann noise limit.

Classical physics doesn't allow you to build this gizmo:

so maybe a noiseless system is possible as well?

Best regards, Piotr

It should be possible to make a combo: the JFET one as a gate supply circuit for a very low R_DS_ON MOSFET for high-power applications. Thermocouples can produce helluva amps, wasting them is a pity. The JFET is switching voltage, the MOSFET is switching current, so to speak...

Best regards, Piotr

There isn't a lower limit, tunnel diodes can do audio too.

piglet

Undoubtedly correct, but IMHO this is pretty pointless given the required LC physical size. RC wins there.

Best regards, Piotr