Abstract: The invention concerns an integrated circuit comprising a resonant circuit (L,20) for receiving by electromagnetic induction an alternating voltage (V.sub.ac), the resonant circuit comprising at least one capacitance (C1-Ci) switchable by means of a programmed switch (11), the switch comprising a circuit breaker (7), a memory cell (6) and a circuit (31, 32, 33, 42) for controlling the circuit beaker (7), the control circuit being supplied by the alternating voltage (V.sub.ac) and arranged for opening or closing the circuit breaker (7) depending on the programming or the erasing status of the memory cell (6).

Abstract: A microcircuit with two contact and non-contact operating modes, including communication device (2) specific for the non-contact operating mode, communication device (3) specific for the contact operating mode, electronic circuit (4) common to both operating modes, a coil (L) for receiving an AC voltage (Va) by induction, a rectifier circuit (Pd) for rectifying the AC voltage (Va) to give a first microcircuit power supply voltage (Vcc1), at least one power supply contact (p1) for receiving a second microcircuit power supply voltage (Vcc2) a distribution line (5) for distributing the first (Vcc1), or second (Vcc2) power supply voltages, a switch circuit (6, 13) between the power supply contact (P1) and the distribution line (5), and controller (7, 8) for controlling the switch circuit, which controller (7, 8) are arranged to sense the AC voltage (Va) across the terminals of the coil (L), and close the switch circuit (6, 13) when the second power supply voltage (Vcc2) is present on the power supply contact, or

Abstract: An integrated circuit (30) for non-contact operation by means of at least one coil (L) forming a tuned resonant circuit with a tuning capacitor (C.sub.A), including a charge pump (10) with two clock inputs (E.sub.1 E.sub.2), wherein the clock inputs (E.sub.1 E.sub.2) of the charge pump (10) are constantly connected to the terminals of the coil (L), at least during the periods of non-contact operation of the integrated circuit, whereby the charge pump, seen from the clock inputs thereof, is a constant component of the tuning capacitor of the tuned resonant circuit.