Re: micro power square wave oscillator

On Tue, 01 Jul 2008 18:05:58 -0700, D from BC
<myrealaddress@xxxxxxxxx> wrote:

<snip>
I was thinking of loading too..
Mmmmm....
1/100Khz = 10uS

Let's say a risetime and falltime of 1uS.
Say supply = 5V

By
I = C dv/dt
And assuming a 100% efficient circuit..

10uA = C 5V/1uS

C = 2pF !!

With those assumptions and if I did the math right, it suggests you
can't even drive a typical scope probe without going over the supply
current spec.

I suppose you are right. Dispels the PUJT relaxation thingy, I think,
as it dumps the charge each cycle and I think the 2n6028 has 100's of
pF, roughly. Not good.

Trapezoidal rise/fall, then? ;) Or perhaps draw some charge at first
and then just move it back and forth in an LC + xtl tank with high Q,
replacing losses?

How do the watch folks do it? There must be some serious remodeling
of crystals for simulation work there (vastly more complex
understanding of them) in order to design something as efficient as
I've seen from them. Anyone know the details here?

Jon
.