GB1437981A - Circuits for performing mathematic functions - Google Patents

Abstract

1437981 Multipliers and dividers RICOH KK 1 May 1973 [1 May 1972] 20622/73 Heading G4G An arithmetic circuit comprises resistances connected in two parallel circuits each having a constant current source, the first circuit providing a source of constant voltage for application to the second. As shown, R ZD , ZD and Tr 1 maintain a constant voltage across R 1 whereby these elements together provide a constant current through R 2 The circuit R 1 , R 2 , Tr 1 together with Tr 2 provides a constant voltage across R 3 Hence a constant current is maintained through R 0 , so that: E 0 #(R 2 .R 0 )/ (R 1 .R 3 ).E 1 . By varying some of these resistances and keeping others constant various division and multiplication operations may be performed. In the modification of Fig. 2, the accuracy of the circuit is improved by supplementing the transistors Tr 1 , Tr 2 by differential amplifier circuits of unit gain, respectively A1, Tr 1 <SP>1</SP> and A2, Tr 2 1. In a practical version of the circuit (Fig. 4, not shown), the resistances R 2 , R 3 are variable and are constituted by D/A converters in which input quantities A and B are entered. An analogue voltage representing A/B is derived as the output of amplifier A3 and is applied to one terminal of a comparator the other output of which is connected to a D/A converter. The latter is connected to a counter driven by a clock-pulse source which is turned off when the inputs to the comparator become equal. The contents of the counter then indicate A/B.