Patent GB-940676-A (GB)
Title: Electronic analog multiplier
IPC: G06G7/164
Filed: 1960-08-09
Abstract: 940,676. Electric analogue calculating. A. NATHAN. Aug. 9,1960 [Sept. 2, 1959], No. 27595/60. Heading G4G. An electronic analog multiplier produces an output signal representing the instantaneous product of variables x, y and comprises first electronic generating means including at least one electronic squaring means receiving plural input potential signals which are linear functions of the input variables to produce therefrom plural secondary signals of potentials representing wherein c, k are constants, U represents plural other constant values and or second generating means comprising first squaring means having a transfer property such that an addition voltage simultaneously applied to all the input terminals thereof is substantially transferred to its output terminals connected to the first generating means,and including plural nonlinear conductive means having a common output connection, with each adapted to receive a corresponding secondary signal, and with current means connected to such common connection which are adapted to supply all of the current flowing therefrom into the conductive means at a given instant and to produce thereat the required output signal. Fig. 3 shows a multiplier producing a voltage e 0  = kz = kxy comprising triode cathode followers 14, 16, 18, 20 receiving respectively a constant voltage -v over linear resistor 1 and potentiometer 2; analog voltages x,-y over linear resistors 3, 4 and constant voltage v over linear resistors 5, 6; analog voltages x, y over linear resistors 7, 8 and constant voltage -v over linear resistors 9, 10; and analog voltage x over linear resistor 11 and constant voltage -v over linear resistors 12, 13. The several cathode followers feed signals e 11 , e 12 , e 21 , e 22  which are linear functions of the input signals, to squaring networks r 11 , r 12 , r 21 , r 22  comprising linear and voltage dependent parallel resistors returned in pairs to a voltage source V over resistors 22, 23 which also operate to transfer additive voltages applied to the input terminals of the squares to the output terminals thereof. The outputs of r 11 , r 12  are combined at the input of cathode follower triode 24 and those of r 21 , r 22  at the input of cathode follower 26; the cathode signals e 1 , e 2  being fed over similar squaring networks to the input of cathode follower triode 29 across whose cathode resistor 30, 31 the required output voltage e 0  is developed. where x, y are the input variables and z is the output variable in three dimensional coordinates and u, v are corresponding rectangular coordinates having axes at 45 degrees to the x, y coordinates (Fig. 1). Then e 11 , e 12 , e 21 , e 22  represent the tangential planes to the surface z = xy at points O, D, F, E while e 1 , e 2  represent the tangential planes to z = xy along OD and FE for instantaneous values of x, y given by 2uU - v<SP>2</SP> - u<SP>2</SP> + k Specification 940, 677 is referred to, and the operation of the apparatus is explained with reference to a complex mathematical analysis. A modified circuit (Fig. 4 not shown) utilizes diodes in series with resistors as the non linear circuits.