[time-nuts] Advantages of differential oscillator structures?

Bob Camp lists at rtty.us
Sat Aug 10 15:41:12 UTC 2013


Hi

I suspect that built from discrete parts you will simply have an audio / square wave oscillator. It's a classic multivibrator circuit….

Bob

On Aug 10, 2013, at 11:13 AM, Azelio Boriani <azelio.boriani at screen.it> wrote:

> Build it from discrete parts, of course, what frequency do you suggest
> to try? 32768Hz, 1MHz? I have nothing in-between...
> 
> On Sat, Aug 10, 2013 at 5:04 PM, Magnus Danielson
> <magnus at rubidium.dyndns.org> wrote:
>> On 08/10/2013 12:10 PM, Attila Kinali wrote:
>>> On Sat, 10 Aug 2013 02:39:35 -0700
>>> wb6bnq <wb6bnq at cox.net> wrote:
>>> 
>>>> I gather you did not fully read the paper ?
>>> I did, but...
>>> 
>>>> This paper presents a circuit topography that allows the low current
>>>> operation at a high frequency (12.8 MHz) thus reducing complexity.  This
>>>> in turn allows the design and manufacture of a radio system using one
>>>> crystal oscillator at a frequency of 12.8 MHz (example in the paper)
>>>> with the low power advantage that previously required two oscillators.
>>> That's one advantage, and not a small one, but differential oscillators
>>> have been in use earlier and even in places where power consumption did
>>> not matter much. It pops up in crystal oscillator designs now and then
>>> but without any mention why this architecture was choosen. So i started
>>> to wonder whether there was any additional advantage than just lower
>>> power consumption and being able to work with less headroom, like better
>>> phase noise or better long term stability or less harmonics.
>> Well, at least from this paper they have not analyzed that. Here they
>> only use it for it's benefits in power, which is obvious from the Abstract.
>> 
>> If you wish to know other benefits, they need to be analyzed separately,
>> which by itself might prove an interesting paper. Reducing current drawn
>> should be interesting, as this should reduce 1/f noise in the feedback
>> amp, which should make the 1/f^3 noise lower significantly, which should
>> be beneficial for the stability of the oscillator in noise terms,
>> however it might not be beneficial for the oscillator in systematic
>> frequency drift terms. As always, it's a balance thing.
>> 
>> It should not be too hard to build it, try it, measure it and learn from
>> it. Sounds like fun!
>> 
>> Cheers,
>> Magnus
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