Abstract: The transistor comprises two electrodes, (source (22) and drain (23), with a semiconductor tunnel channel (21A, 21B) arranged therebetween. A gate (24) for applying control signals is coupled to the channel. The semiconductor channel consists of a plurality of regions differing in their current transfer characteristics: contact regions (21c), connected to the source and drain electrodes, and a tunneling region (21t) arranged between the contact regions. The energy of free carriers in the contact regions differs from the energy of the conduction band or the valence band of the tunneling region which forms a low energy tunnel barrier the height (.DELTA.E) of which can be modified by control signals applied to the gate. The operating temperature of the device is kept sufficiently low to have the tunnel current through the barrier outweigh currents of thermionically excited carriers.

Abstract: Two Josephson gates are connected in series to a low impedance voltage source. Each junction is bridged by a load impedance. The feed voltage is maintained in the order of the gap voltage which corresponds to the voltage drop across a Josephson junction when it is in its single-particle-tunneling state. Therefore, only one out of both Josephson elements can exist in the voltage state at a time, and the other junction is forced to assume the superconducting pair-tunneling state.In its symmetric form, the basic circuit can be used as flip-flop or storage means. If asymmetric, the basic circuit shows monostable switching behavior, and it can be used as logic gate. Circuit asymmetry can be caused either by design using different junction areas or electrically by proper bias control currents applied to either or both gates of the basic circuit. The degree of symmetry or asymmetry can even be shifted with electrical means.