[hpsdr] ADG901

[Dan Andersson]

On Tuesday 16 January 2007 04:29, Geoff wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Guys,
>     A couple of numpty questions (I fix machines for a living). Has
> anybody looked at the Analog Devices ADG901 as a QSD Switch? I can´t
> recall seeing it on the list. Has anybody identified a class of
> flip-flops suitable for QSD service above 30 or 40 MHz?
>
>     73 de Geoff vk2tfg.
> 


Geoff,

The ADG901 is on the slow side for Ton and Toff.

If you get rid of your fear of ECL logic, you will find the AUC1G66 from Texas 
Instruments able to switch faster. These are singles so look at the 
sn74auc2g53's as well.

TI also have a range of flip flops well up in the GHz range to drive these 
switches.

You just have to think "50 Ohms" when designing with ECL ( PECL ) and be 
careful in the power feed. If you run these switches on 3.3V instead of 1.8 
or 2.5V, you "press down" the max values for Ton and Toff towards and below 
2nS.

So please! Don't write off the ECL technology just because it's an old 
technology. We used to be able to build rather nift computers with them, Like 
VAX11 and PDP11's... And the last VAX'es was real beasts regarding speed.

I wired me a SoftRock with these chips ( sn74auc2g53 ) and the MC10EP131 flip 
flop, also from TI.


Some thoughts from an old guy... :)


//Dan



-- 
Dan Andersson, M0DFI
dan at andersson.co.uk                         dan.andersson at ieee.org


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