Sense amplifier circuit implemented by bipolar transistor and improved in current consumption

A semiconductor memory device fabricated on a single semiconductor chip, comprising:

• a) a memory cell array for storing a plurality of data bits;
• b) a plurality of digit line pairs coupled with said memory cell array;
• c) a plurality of word lines coupled with said memory cell array and operative to allow said data bits to be selectively read out from said memory cell array to said plurality of digit line pairs;
• d) a plurality of differential amplifier circuits selectively activated with a decoded address signal, and each having first and second bipolar transistors controlled with an input differential voltage signal indicative of one of said data bits and supplied to the base nodes thereof, and a first constant current source coupled between the emitter nodes of said first and second bipolar transistors and a first constant voltage source, said first and second bipolar transistors allowing first and second branch-currents to respectively pass therethrough;
• e) a pair of interconnections respectively coupled with the collector nodes of said first and second bipolar transistors,
• f) a current-to-voltage converting unit having a first series combination of a first resistive element and a third bipolar transistor associated with said first bipolar transistor and coupled between a second constant voltage source and one of said pair of interconnections, a second series combination of a second resistive element and a fourth bipolar transistor associated with said second bipolar transistor and coupled between said second constant voltage source and the other of said pair of interconnections, and a third constant voltage source coupled with the base nodes of said third and fourth bipolar transistors for producing an output differential voltage signal at the collector nodes of said third and fourth bipolar transistors;
• and
• g) a source of standby current associated with said first and second series combinations;
• and having a second constant current source coupled with said first constant voltage source, and distributing means coupled between said pair of interconnections and said second constant current source and operative to allow third and fourth branch-currents to flow from said third and fourth bipolar transistors to said second constant current source, said distributing means controlling the amount of said third branch-current and the amount of said fourth branch-current depending upon a differential voltage between said interconnections so that said first and second branch-currents are inversely proportional to said third and fourth branch currents, respectively.

A sense amplifier circuit comprising:

• a) a differential amplifier circuit having first and second bipolar transistors controlled with an input differential voltage signal supplied to the base nodes thereof, and a first constant current source coupled between the emitter nodes of said first and second bipolar transistors and a first constant voltage source, and activated with an activation signal for allowing first and second branch-currents to respectively pass through said first and second bipolar transistors,
• b) a pair of interconnections respectively coupled with the collector nodes of said first and second bipolar transistors,
• c) a current-to-voltage converting unit having a first series combination of a first resistive element and a third bipolar transistor associated with said first bipolar transistor and coupled between a second constant voltage source and one of said pair of interconnections, a second series combination of a second resistive element and a fourth bipolar transistor associated with said second bipolar transistor and coupled between said second constant voltage source and the other of said pair of interconnections, and a third constant voltage source coupled with the base nodes of said third and fourth bipolar transistors for producing an output differential voltage signal at the collector nodes of said third and fourth bipolar transistors;
• and
• d) a source of standby current associated with said first and second series combinations, and having a second constant current source coupled with said first constant voltage source, and distributing means coupled between said pair of interconnections and said second constant current source and having a first diode element coupled between said one of said interconnections and said second constant current source and a second diode element coupled between said other of said interconnections and said second constant current source so as to allow third and fourth branch-currents to flow from said third and fourth bipolar transistors to said second constant current source, said first and second branch currents being inversely proportional to said third and fourth branch currents, respectively.