[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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