Apparatus for maintaining a low power loss within an input stage for digital signals

US5304858A · kind A · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventors

• Herbert Heitzer · Amberg, DE
• Gerhard Rumold · Bubenreuth, DE

Key dates

• Filing date: Jul 14, 1992
• Grant date: Apr 19, 1994
• Expiry date: Jul 14, 2012

Classification

• Technology area (CPC G): Physics
• CPC primary: G05F1/618
• WIPO field: Control
• WIPO sector: Instruments

Abstract

An input stage for programmable controllers in which a Schmitt trigger and a two-terminal configuration having a negative resistance characteristic are combined in an integrated circuit. A first resistor supplementing this bipolar configuration to form a constant-current sink is connected externally of the integrated circuit in parallel with the bipolar configuration. A power loss mainly develops in the first resistor which is external of the integrated circuit so that multi-channel input stages are able to be realized cost-effectively without requiring a supply of cooling air to cool the integrated circuit. A second resistor may be connected external of the integrated circuit in series with the two-terminal configuration to further reduce power loss within the integrated circuit and to limit the current flowing into the integrated circuit.