A mixer of the two-transistor type (T.sub.1, T.sub.2) arranged in series by a source S.sub.2 and a drain D.sub.1. A Gate G.sub.1 receives a radio frequency signal RF and a gate G.sub.2 a local oscillator signal L0. Matching networks R.sub.1 and R.sub.2 are provided for the respective signals RF and L0. One element of the network R.sub.3 positioned at the output (drain D.sub.2 of the transistor T.sub.2) restores a short-circuit at the frequency f.sub.L0 of the local oscillator. The instability of the input G.sub.2 of the transistor T.sub.2 is compensated for by an inductor element L inserted between the junction point of the source S.sub.2 and the drain D.sub.1 and the common-mode pole.