Temic Telefunken Microelectronic Gmbh

Jurgen Schnabel

Hermann Hammel

Henrik Gutsch

Horst Hafner

Friedemann Schmidt

Wolfgang Roper

Joachim Kuhnle

In order to protect against any damage caused by electrostatic discharges, an integrated circuit layout is provided with at least one circuit connection which is connected via one of two diodes, respectively, to a first supply line and a second supply line. The diodes are reverse biased, i.e., one of them becomes conductive if a potential exists at the circuit connection that is either higher or lower than the supply potentials applying to the supply lines. The circuit layout is provided with an overvoltage suppression device connecting the two supply lines. The overvoltage suppression device is switched into a low impedance state by a steep rate increase or rise in a supply voltage applied between the supply lines such that a discharge current counteracting the increase in the supply voltage will flow via the overvoltage suppression device from the one supply line to the other supply line, and the discharge energy is converted into heat in the overvoltage suppression device.

Electrostatic discharge circuit layout

A switch is described with a bipolar transistor as first switching element having a high breakdown voltage when operated in the reverse direction. This can be accomplished by a second switching element provided in the switch, a switching transistor, e.g. an MOS transistor, through which the base and the collector of the bipolar transistor are joined together, is activated in the reverse mode of the switch, i.e. when the bipolar transistor is in inverse mode, in such a way that the second switching element becomes conductive. The collector-emitter breakdown voltage of the bipolar transistor, i.e. its maximum permissible collector-emitter voltage, is thus brought closer to its higher base-emitter breakdown voltage.

Switch with a first switching element in the form of a bipolar transistor

A speakerphone for a telephone circuit includes an output stage that comprises a loudspeaker amplifier coupled to a loudspeaker through a coupling capacitor. An auxiliary circuit includes a reference input element that provides first and second reference voltages which are used to charge the coupling capacitor to a given level prior to the input signal being coupled to the loudspeaker through the coupling capacitor to insure a click-free switch-on of the loudspeaker.

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Jurgen Schnabel