Current mode logic circuit
AssigneeMotorola, Inc.
InventorsFrank J. Swiatowiec, Ramachandra A. Rao
Life of this patent
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Abstract
A current mode logic circuit providing AND/OR type functions wherein "0" voltage level changes and spikes are substantially eliminated without sacrificing switching speeds by omitting conventional emitter and collector-dotting between the logic input gates and an emitter-follower output stage. The input gates employ diode loads for generating reduced signal swings for driving the output gate. The output gate contains more devices than a single emitter-follower output stage, but the reduced signal swing and a push-pull drive mode for the output gate offsets any increased switching times due to the greater number of devices and thus achieves the overall objectives without any overall sacrifice in switching speed.
Claims6
A non-saturating logic circuit comprising:
- a. an M number of current mode input gates, each current mode input gate including a group of common collector node input logic switching transistors, and an interconnected reference voltage switching transistor;
- b. a first node logic connection, the reference voltage switching transistor associated with each of the M input gates being collector dotted to the first node logic connection;
- c. a current mode output gate, the output gate including an input switching transistor coupled to the first node logic connection and M interconnected selectively enabled reference transistors;
- d. a first load diode coupled to a reference voltage source means and to the first node logic connection for establishing a logic level signal swing at the input switching transistor of the output gate in response to the application of input logic signals to the input gates;
- e. each of the M reference transistors of the output gate being coupled, respectively, to one of the group of common collector node input logic switching transistors so as to be selectively enabled;
- and
- f. the output gate being responsive to a logic level signal swing at the first node logic connection and to the selective enabling of the M reference transistors for generating an output logic level signal.
Dependencies are inferred from the claim text.