Current comparator circuit

A symmetrical current comparator circuit for responding to the difference between first and second current sources, said sources having a common return point, said circuit comprising:

• means for coupling first and second nodes of said circuit to said first and second current sources respectively;
• current mirror means coupled between said first and second nodes and said common return point, said current mirror including a pair of transistors having their emitters coupled together and to said common return point, their bases coupled together, and their collectors coupled respectively to said first and second nodes, and level shifting means coupled from each of said collectors of said pair to said bases of said pair, said current mirror acting to force equality between the currents flowing in said first and second nodes;
• and
• first and second output transistors each having an emitter, a base, and a collector, the base of said first output transistor and the emitter of said second output transistor being coupled to said first node, the base of said second output transistor and the emitter of said first output transistor being coupled to said second node whereby the collectors of said output transistors constitute the output of said circuit.