GB1147797A - Improvements in or relating to analog-to-digital converters - Google Patents

Abstract

1,147,797. Analogue-digital converters. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 12 April, 1966 [15 April, 1965], No. 15984/66. Heading G4H. An analogue-digital converter giving a binary coded output includes a capacitor resistance circuit C 2 R 3 (Fig. 6), to which is applied the unknown analogue signal, the exponentially decreasing voltage as the capacitor discharges being fed to four tunnel diodes Tu1-Tu4 in a quantization circuit Q at times t 0 , t 0 + T, t 0 + 2T ... chosen so that the voltage is halved during each interval T. If the analogue input signal has a value of five volts (Fig. 8, not shown) the first Tu1 of the tunnel diodes Tu1-4 enabled at time t 0 by a first clock pulse at terminal II changes state to apply an output pulse via diode D7 and gate S2 (enabled by a clock pulse at terminal 1 occurring simultaneously with a pulse from the circuit Q to change over a tunnel diode Tu 5 ) to a subtraction circuit M and to an output channel DA. This pulse causes a sudden withdrawal of charge from the circuit R3, C2 and hence a reduction in the voltage applied to the tunnel diodes Tu1-Tu4. On the occurrence of the next clock pulse on terminal II at time t 0 + T none of the tunnel diodes change their state (Fig. 8, not shown) and hence no output pulse is applied. On the third clock pulse at time t 0 + 2T the third tunnel diode Tu3 changes state to give an output pulse and consequently the charge on capacitor C2 is reduced to zero. The output pulses at terminal DA commence with the least significant bit. A further embodiment (Fig. 11, not shown) is described in which the output pulses depend on the state of a bi-stable device at the times T, 2T ....