GB1394809A - Integrated circuit for digital-output meters - Google Patents

Abstract

1394809 Analogue-to-digital conversion INTEGRATED PHOTOMATRIX Ltd 15 Feb 1974 7095/74 Heading G4H [Also in Division H3] In an analogue-to-digital converter, e.g. of the dual ramp type, a single metal-oxide-semiconductor integrated circuit contains analogue circuitry having amplifiers for integrating and comparing analogue quantities, offset correction circuitry for the amplifiers and logic circuitry for counting, clocking and gating. In Fig. 1, clock pulses from generator 1, divided at 5, are continually fed to a counter 10. The input voltage V in is integrated (up) for the time interval from one overspill of the counter to the next, whereupon a reference signal I R is integrated (down), the counter being read-out into a shift register 8 when a comparator 24 detects zero crossing. The integrator 23 and comparator 24 comprise respective long tailed pair MOST amplifiers, Fig. 3, not shown, the voltage on the gate 57, 57<SP>1</SP>, Fig. 2, of the tail MOST, held by capacitor 58, 58<SP>1</SP>, being adjusted after every coding operation, MOST gates 60, 60<SP>1</SP> being enabled during the time interval between zero crossing detection and the next overspill of the counter 10. The whole of the Fig. 1, circuitry, including the multiplexer 19 for transferring the outputs 18 to the display (not shown), excepting the correction capacitors 58, 58<SP>1</SP> and integration capacitor 44 is on a single MOS chip.