Patent GB-1268095-A (GB)
Title: Integrated circuit
Inventor: KRAM WILLIAM PHILIP
IPC: H01L21/00
Filed: 1969-04-01
Abstract: 1,268,095. Integrated circuits. GENERAL ELECTRIC CO. 1 April, 1969 [29 April 1968], No. 17091/69. Heading H3T. [Also in Divisions H1 and H2] A monolithic integrated circuit device comprises one or more integrated circuit elements 4 (Fig. 1), a unidirectionally conductive integrated circuit element D2 connected to device D.C. for supplying the elements 4 at least one of the elements D2, D4 having a region of opposite conductivity type to a substrate portion 20 so as to form a PN junction 22 with the substrate, a circuit point 3 which for one polarity of voltage applied to the terminals 1, 2 achieves the most extreme potential condition of opposite polarity to the polarity of the conductivity type of the substrate and means 26 connecting the circuit point 3 to the substrate so as to reverse bias the PN junction upon application of the one polarity to the terminals 1, 2. The connecting means 26 is such as to co-operate with the PN junction 22 when the other voltage polarity is applied to the terminals 1, 2 to ensure that the PN junction 22 is not forward biased beyond the knee of the forward voltage v. current characteristic of the PN junction. When the polarity of terminal 2 of the A.C. supply S is negative, diode D2, which may be a Schottky diode, conducts and charges capacitor C terminals 3, 5 negative, positive respectively. The avalanche type reverse voltage diode D1 across the supply S limits the voltage to which capacitor C can charge. Resistor 26 is provided to limit the current through isolation PN junction D22 when the terminal 2 of the supply S changes from positive to negative as without sufficient resistance 26 (24, Fig. 4, not shown), the isolation junction D22 would be temporarily forward biased. The resistor 26 reduces the current flow through the isolation junction or substrate diode D22 to a level such that carrier injection at the substrate diode is insufficient to cause harmful parasitic effects in the circuit: The resistor 26 prevents the forward voltage across substrate diode D22 from exceeding, e.g. 0À3 volts or 0À6 volts for a substrate of germanium or silicon where the knee occurs in the forward current-voltage curve for the substrate diode D22. During the half-cycle of the supply S when the terminal 2 is positive the point 3 is the most negative in the circuit connected to the substrate diode D22 which is reverse biased under these conditions. The avalanche type diode D1 conducts in the forward direction when terminal 2 is positive but diode D2 prevents the capacitor C from completely discharging. The diode D2 may be replaced by a transistor (Q1, Figs. 7 and 8, not shown), having its base connected to terminal 3, its collector connected to terminal 2 and its emitter connected to the substrate for inverse mode operation. Alternatively, the collector and emitter connections may be interchanged. When the terminal 2 goes negative greater than terminal 3, the transistor collector emitter path conducts to shunt the substrate diode D22 and prevent it becoming forward biased by clamping the most negative potential at 2 to the P-type substrate.