Current-mode logic circuit

• US 5,550,491 A
• Filed: 09/21/1995
• Issued: 08/27/1996
• Est. Priority Date: 09/28/1994
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Furuta, Koichiro
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): Sanders, Andrew
• Application Number:
  US08/531,931
• Time in Patent Office: 341 Days
• Field of Search: 326/112, 326/115, 327/51, 327/52, 327/65, 327/94, 327/96, 327/103, 327/109, 327/127
• US Class Current: 326/115
• CPC Class Codes: H03K 17/693 Switching arrangements with several input- or output-terminals, e.g. multiplexers, distributors logic circuits H03K19/00; code converters H03M5/00, H03M7/00
• CPC Class Codes: H03K 19/01721 by means of a pull-up or down element
• CPC Class Codes: H03K 19/09432 with coupled sources or source coupled logic H03K19/096 takes precedence
• CPC Class Codes: H03K 3/356034 the input circuit having a differential configuration

Abstract

A current-mode logic circuit is provided having large gain and resistance to noise or power source fluctuations which employs in its logic circuits circuits that shape waves. Such a current-mode logic circuit entails little increase in the area of integrated circuits. In addition to a differential logic pair composed of MOS transistors M31 and M32, load elements R31 and R32, and constant-current source I31, the current-mode logic circuit of the present invention is provided with a holding transistor pair composed of MOS transistors M33 and M34. MOS transistors M31 and M32 have equal conductance, and MOS transistors M33 and M34 have equal conductance. In addition, the present invention is characterized in that the sum of conductance of MOS transistors M31 and M33 is a constant if the electrical power consumption of the circuits is constant.

Claims

1. A current-mode logic circuit comprising:

a differential logic pair that is composed of a first logic means for controlling conductive or nonconductive states between a first output line and a constant-current source by means of an input signal or its reverse signal and a second logic means for controlling the conductive or nonconductive states between a second output line and said constant-current source by means of said input signal or its reverse signal;

equivalent conductance of said first and second logic means being equal and, in response to said input signal or its reverse signal, conductive or nonconductive states of said first and second logic means acting with complementary logic; and

comprising a holding transistor pair that is composed of a first MOS transistor having its gate electrode connected to said second output line, its drain electrode connected to said first output line, and its source electrode connected to said constant-current source, and a second MOS transistor having its gate electrode connected to said first output line, its drain electrode connected to said second output line, and its source electrode connected to said constant-current source;

said first and second MOS transistors having equal conductance.

2. A current-mode logic circuit according to claim 1 wherein said first and second logic means are MOS transistors that input to their gate electrodes said input signal or its reverse signal.

3. A current-mode logic circuit according to claim 1 wherein said input signal or its reverse signal is a combination of a plurality of input signals or their reverse signals, and said first and second logic means are series-parallel connected MOS transistors that input to their gate electrodes said plurality of input signals or their reverse signals.

4. A current-mode logic circuit according to claim 1 wherein conductance of said first and second MOS transistors is greater than equivalent conductance of said first and second logic means.