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Sample and Hold for Analog To Digital Conversion

IP.com Disclosure Number: IPCOM000082740D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 43K

Publishing Venue

IBM

Related People

Herrell, DJ: AUTHOR

Abstract

A sample and hold scheme for Josephson analog-to-digital (A/D) converters, which will achieve narrow sampling windows is outlined in what follows.

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Sample and Hold for Analog To Digital Conversion

A sample and hold scheme for Josephson analog-to-digital (A/D) converters, which will achieve narrow sampling windows is outlined in what follows.

The present approach utilizes the concept that the analog signal is first converted to a digital form, and then the necessary logic is employed to convert the digital signal to the necessary binary code.

Consider an A/D of four bits; this corresponds to 16 distinct levels of the input analog data and one Josephson gate per level of input analog data, as shown in Fig. 1, may be utilized. The string of Josephson gates J1-J16 is supplied with current, I, and the threshold of the gates J1 through J16 is adjusted through the use of the biases b1 to b16.

As a result, the effective gain curves appears as shown in Fig. 2, and each gate would have control current thresholds of T1 through T16. The maximum range of the input analog data is indicated by R in Fig. 2. Thus, the analog data applied to the control line (a) of Fig. 1 moves the operating point anywhere between the points A and B of Fig. 2; which are likewise separated by R.

At this point gates J1 to J16 will not switch. A strobe pulse applied via strobe line in Fig. 1 is now required which propagates as a step with a fast rise time, delta t, generated by a small Josephson junction. With a delay of T at the bottom, an effective strobe pulse of width tau is generated (Fig. 3). Operation.

With a data input corresponding, for example, to 3.5 unit current inputs, the starting point is at C in Fig. 2. The strobe pulse is applied and moves the operating point through T1, T2 and T3 to point D and back to point C - all within a time of T + delta t.

Gates J1, J2 and J3 switch to the V not = 0 state provided the strobe pulse is sufficiently long, such that...