Abstract: A semiconductor switching network is disclosed in which complementary bipolar transistors are employed as "floating" crosspoints. Each crosspoint consists of a pair of complementary bipolar transistors with each transistor being connected in series with one of the leads of the communication pair. Each one of the complementary bipolar transistors is, in turn, surrounded by a "protective control shell" of diodes and transistors which provides the crosspoint with overvoltage and reverse voltage protection and secures crosspoint turn-off. Additionally, the protective control shell contains a self-bias arrangement to eliminate the need for external power supplies to operate the crosspoint as well as an optoisolator control circuit to eliminate direct connections to external control circuits.

Abstract: Signal transmission circuit characteristics are supplemented by a negative conductance circuit in which current sources of complementary polarity are connected in shunt between the conductors of the signal circuit. Changes in the voltage level of one side of the signal circuit are sensed at a point common to the two sources and applied through a positive impedance to control the current output magnitude of one of the sources for effecting a supplementing of the signal circuit current as though the changed voltage level had been applied in the presence of a negative form of that impedance connected at that common point.In additional embodiments, different, or variable, positive impedance are connected in the sensing circuit output coupling to cause the negative of such impedance to appear at such signal circuit terminal.

Abstract: Improved current mirrors are provided by connecting current mirrors of known types in cascode.