Abstract: A converter, transmitter and/or receiver for mixing an input signal (I.sub.RF) having a first frequency (RF) with an input signal (I.sub.LO) coming from a local oscillator having a second frequency (LO), and for producing an output signal (O.sub.IF) having an intermediate frequency (IF), with rejection of the harmonics of the second frequency (LO) up to a very high order, for example, higher than the tenth order. The device includes a double balanced ring mixer (17) of field effect transistors (12, 13, 14, 15), having a first and a second pair of input terminals (3, 4; 1, 2) and having a pair of output terminals (5, 6), and a first and a second coupler (18, 19) respectively acting as a phase separator and phase combiner for the input signal (I.sub.RF) having the first frequency (RF) and output signal (O.sub.

Abstract: The invention relates to a semiconductor device including an amplifier, and a mobile telecommunication terminal comprising this semiconductor device. The amplifier has a very high frequency a.c. signal and comprises a last stage but one of depletion-layer MESFET transistors (T3) and a last transistor stage (T4) of the same type, coupled by a d.c. isolation capacitor (C4). This capacitor (C4) forms with the intrinsic diode (.increment.4) of the transistor (T4) of the last stage a series-arranged rectifier circuit. The latter imposes a shift of the mean level of the a.c. signal on the terminals of said isolation capacitor once the amplitude of the positive part of this a.c. signal has exceeded the conduction threshold of the intrinsic diode (.increment.4). This shift of the mean level (-1.5 volts) is used as a negative voltage (-VG) for biasing the coupled gates of all the stages of the amplifier circuit.