The passive transponder comprises an antenna (2) connected to an integrated circuit (6) the analogue part of which includes a passive voltage rectifier (8) supplying a rectified voltage (V.sub.DC1) and an active multiplier or booster (16) for said rectified voltage which is formed by a capacitor (C2) switched to a relatively low frequency, for example 1 MHz, by means of switches formed by transistors (18 to 21) controlled using an oscillator (24).