An envelope detector circuit, suitable for use in RFID tags, includes a voltage doubler circuit and a biasing voltage generating circuit which comprises components matched respectively to rectifying components of the voltage doubler circuit. A rectifying component of this voltage doubler circuit is formed by a transistor controlled by the biasing voltage generating circuit which provides a biasing voltage to a control gate of this transistor, the biasing voltage generating circuit being arranged so as to permit a determined forward biasing current to flow through the transistor and further rectifying elements of the voltage doubler circuit. This embodiment provides fast, highly sensitive detection of envelope waveforms in input signals. Thanks to the matched rectifying components, efficiency variations due to variations in manufacturing process can be eliminated. The envelope detector circuit is further arranged for maintaining a stable detection independent of variations in temperature.