[time-nuts] Wilkinson TDC

Charles P. Steinmetz charles_steinmetz at lavabit.com
Mon Apr 30 05:40:01 UTC 2012


Bruce wrote:

>The essentials of a Wikinson TDC can be simplified to the attached 
>circuit which only requires the addition of a zero crossing 
>comparator to monitor the voltage across the capacitor C1.
>
>A few refinements to improve the capacitor charging current 
>switching transitions and the addition of an upper voltage clamp 
>together with the use of faster transistors may be useful.

The HFA3096 transistor array (3 NPN + 2 PNP) should do nicely.  My 
simulations show a small but definite improvement in the current 
switching transitions.

BTW, the PNPs in an HFA3096/3128 also pretty much solve the Cb-e 
feedthrough in a Wenzel-style squaring circuit, giving pretty flat 
tops on the high output pulses without resorting to diode isolation 
or other secondary techniques.

Best regards,

Charles








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