Other

Moore Products Co.

Chih C Chang

An apparatus for converting the sum of m digital signals to an analog signal utilizing resistors and switches only. The operating time of the apparatus is the time required to pass the signal through a single switch. This invention can also be utilized in an A/D converter for converting the difference between an analog signal and several digital signals to a digital signal without using extra time to compute the subtraction.

D/A and A/D converters utilizing weighted impedances

An apparatus for adding two binary numbers in which the computation of the sum and the carry propagation are performed in separate parts. The carry propagation passes through switches in a switch network which is controlled by a switch control. The independence of the carry propagation, switch control, carry creation and the computation makes the carry propagation faster than prior art adders without increasing the number of logic gates. The adder can be made in the form of an m bit integrated circuit which can be used as a building block to construct an adder for the addition of a larger number of bits.

Isolated carry propagation fast adder

The ratio C.sub.1 /C.sub.2 between the capacitances of two capacitors is obtained by connecting them into the frequency-determining circuit of an oscillator in at least three different combinations, namely C.sub.1 along, C.sub.2 along and both or neither of C.sub.1 and C.sub.2 ; the resultant oscillation frequencies are measured, and a signal representative of changes in C.sub.1 /C.sub.2 is derived from the oscillator frequencies, preferably by means of digital circuitry. In one preferred mode C.sub.1 /C.sub.2 is obtained by forming signals proportional to ##EQU1## and in another preferred mode proportional to ##EQU2## In still another preferred mode C.sub.1 /C.sub.2 -1 is obtained from the expression T.sub.1 -T.sub.3 /T.sub.2 -T.sub.3 and used as the indication of changes in C.sub.1 /C.sub.2. In the foregoing, f.sub.1, f.sub.2, f.sub.3 and f.sub.4 are the oscillator frequencies produced respectively by connecting C.sub.1 alone, C.sub.2 along, neither C.sub.1 nor C.sub.2, and both C.sub.1 and C.sub.2 into the frequency-determining circuit, and T.sub.1, T.sub.2, T.sub.3 and T.sub.4 are the periods of oscillations at f.sub.1, f.sub.2, f.sub.3 and f.sub.4 respectively.

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Huntingdon Valley, PA, United States of America

Chih C Chang