[time-nuts] Advantages of differential oscillator structures?

Bob Camp lists at rtty.us
Sat Aug 10 09:10:56 EDT 2013


Hi

A couple of observations:

1) There are *way* more low stability oscillators out there than high stability ones. A lot of the papers are focused on applications that are not "TimeNuts" grade.

2) There are way more oscillator circuits out there than time to list them. Given a couple of days, you could probably "invent" a new circuit. 

3) Most circuits you see are grounding or buffering variations of each other. Grounding / layout / component selection can be important. Some circuits are easier to layout with this or that technology. 

4) There are some classic debates about add on stuff. AGC's are the best example. In loop / out of loop buffers are another. There are several others. They really don't change the basic circuit, but they do impact how it does what it does. 

Past that (with one exception) the world has pretty much settled on topologies that have one device as the active element. The reasoning is pretty simple - fewer active devices means less impact of active device noise and tempco. The one exception is the HP bridge circuit that Rick Karlquist came up with. There the idea is to have no active devices in the loop, with some impact on Q. 

There is another exception to the one active device rule, but it's not seen in precision oscillators. As you go lower in frequency, crystal loss goes up. There are cases where you simply can't get enough gain out of a practical circuit using one active device. Since you are at low frequency, the impact of the second active stage is not as great as it would be at HF. The circuit shown in the paper is one of the classic ways to get a low frequency crystal going. It's also a very simple audio square wave oscillator. The paper stuff at the links does indeed go into this issue in some detail. 

Bob 


On Aug 10, 2013, at 4:22 AM, Attila Kinali <attila at kinali.ch> wrote:

> Hi,
> 
> While reading up on oscillator circuits i stumbled over differential
> oscillator structures (see [1] for example). But sofar i have been
> unable to figure out what the exact advantages of a differential
> oscillator strucutre in general are.
> Would someone here be so kind and give me some hints where to look?
> 
> Thanks in advance
> 
> 			Attila Kinali
> 
> 
> 
> [1] "A High-Stability, Ultra-Low-Power Differential Oscillator Circuit
> for Demanding Radio Applications", by David Ruffieux, 2002
> http://www.imec.be/esscirc/ESSCIRC2002/PDFs/C02.01.pdf
> http://www.imec.be/esscirc/ESSCIRC2002/presentations/Slides/C02.01.pdf
> 
> 
> -- 
> 1.) Write everything down.
> 2.) Reduce to the essential.
> 3.) Stop and question.
> 		-- The Habits of Highly Boring People, Chris Sauve
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.



More information about the time-nuts mailing list