[time-nuts] question Alan deviation measured with Timelab and counters

Charles Steinmetz csteinmetz at yandex.com
Sun Jan 25 02:07:54 EST 2015

Stephane wrote:

>I'm now trying to evaluate various architectures of 2-channels 
>squarers and a DMDT. For that I'm designing a PCB with 4 squarers : 
>simple 74ac04 gate biased at VCC/2, a LT1016 comparator, the 
>transistor based differential amplifier from Winzel and the one from Charles.

Note that squaring a 10MHz sine wave and squaring a 10 or 100Hz mixer 
output are two very different tasks.  If you start at baseband, a 
Collins-style multi-stage limiting amp is a great benefit.  That is 
generally not necessary if you start at 10MHz (or if you do use a 
Collins-style limiter it needs far fewer stages).  All of the 
squarers you mention work well at 10MHz, but not as well at baseband.

The LT1719 is easier to apply and faster than the LT1016.  You may 
want to use that instead of the 1016.  The LT1719 and LT1715 
datasheets show the simplest possible implementation (see below).

The MPSH81 devices in my version are available in surface-mount 
(MMBTH81) if that is more convenient.  Other fast transistors will 
also work (BFT92, BFT93, BFG31).

Best regards,


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