Abstract: A spiral resistor being of a type formed on a semiconductor substrate to withstand high voltages, comprises at least one thin field-plate layer covering said substrate between adjacent turns of the resistor. This prevents the well-known phenomenon of the "phantom gate" from occurring which would result in the characteristics of spiral resistors deteriorating over time.

Abstract: A threshold voltage generator for a field-effect transistor, being of a type adapted to compensate for variations of the threshold voltage from a nominal value, comprising a first amplifier having a first input connected to a current generator; a second amplifier connected ahead of a second input of the first amplifier and having an input connected to another current generator; and a third amplifier connected after the first amplifier and having an output adapted to produce the value of said threshold voltage.

Abstract: A telephone subscriber system comprising a speech circuit and a ring circuit adapted to be integrated monolithically to a semiconductor material substrate and being coupled to a telephone subscriber line, respectively through first and second circuit switch of the diode bridge type, further comprises a first circuit changeover switch, under control by the user, which drives at least second and third circuit switching means connected between the first diode bridge circuit and the speech circuit. The third circuit changeover switch is connected to the speech and ring circuits at a circuit communication node which forms the system point of reference, physically coincident with the substrate. The system includes a circuit interface means for controlling the second and third circuit changeover switch by external electrical signals which are related to the circuit communication node.

Abstract: A circuit for synthesizing an impedance associated with a telephone subscriber's circuit connected to a two-wire telephone line is described. The circuit of the invention is adapted to synthesize a complex impedance which can function both as a termination impedance and a balance impedance. The termination impedance utilizes a positive feedback loop structure having a loop gain which is at all times less than unity. The circuit that implements both the termination and balance impedances with sidetone suppression is also described. Each of the embodiments is realizable with a single external component consisting of a resistor.