Protection circuit for electronic components employing bipolar transistors

An electric circuit comprising:

• a plurality of electrical elements in a electric circuit to be protected;
• a plurality of terminals associated with said plurality of electrical elements, said plurality of terminals supplied with operating voltages;
• a protection circuit for protecting said plurality of terminals, said protection circuit-comprising;
• a plurality of first bipolar transistors connected between said plurality of terminals and a first voltage in cascade, bases of said plurality of first bipolar transistors connected in common and supplied with a second voltage;
• and a second bipolar transistor connected between one of said plurality of terminals and said second voltage, a base of said second bipolar transistor supplied with a third voltage lower than said second voltage.

A device comprising:

• a plurality of electrical elements in a device to be protected;
• a plurality of terminals associated, respectively with said plurality of electrical elements;
• a first protection circuit connected to said plurality of terminals for protecting said plurality of electrical elements, said first protection circuit comprising a plurality of first bipolar transistors connected between said plurality of terminals and a first voltage in cascade, bases of said plurality of first bipolar transistors connected in common and supplied with a second voltage;
• and
• a second protection circuit connected to two or more of said plurality of terminals, said second protection circuit comprising a plurality of second bipolar transistors connected between said plurality of terminals and said first voltage, bases of said plurality of second bipolar transistors connected in common and supplied with a third voltage different from said second voltage.

An electric circuit comprising:

• a first electrical element operating within a first voltage area and having a first breakdown voltage;
• a second electrical element operating within a second voltage area and having a second breakdown voltage;
• a third electrical element;
• a first terminal connected to said first electrical element;
• a second terminal connected to said second electrical element;
• a third terminal connected to said third electrical element;
• a first protection circuit connected to said first and second terminals wherein said first protection circuit comprises a first bipolar transistor whose emitter is connected to said first terminal and a second bipolar transistor whose emitter is connected to said second terminal, and wherein bases of said first and second bipolar transistors are connected in common;
• a second protection circuit connected to one of said first and second terminals, wherein said second protection circuit comprises a third bipolar transistor whose emitter is connected to said third terminal, wherein a base of said third bipolar transistor is electrically isolated from said bases of said first and second bipolar transistors.