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Differential Complementary Metal Oxide Semiconductor Logic Circuits

IP.com Disclosure Number: IPCOM000115260D
Original Publication Date: 1995-Apr-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Bartling, SC: AUTHOR [+4]

Abstract

Disclosed is a Complementary Metal Oxide Semiconductor (CMOS) Device that performs a N transistor logic function similar to a CMOS sense amp. This combination results in a fast logic gate when compared to similar dynamic logic families.

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Differential Complementary Metal Oxide Semiconductor Logic Circuits

      Disclosed is a Complementary Metal Oxide Semiconductor (CMOS)
Device that performs a N transistor logic function similar to a CMOS
sense amp.  This combination results in a fast logic gate when
compared to similar dynamic logic families.

      The Sense Amp Xor (Figure) has N-tree evaluate stack that
performs the xor function using true and complement inputs and a N
channel precharge network that precharges the dynamic node to Vdd-Vt.
The cross coupled P channel devices hold the charge on the dynamic
node until all input signals evaluate to Vdd or Gnd.

      In the precharge operation xclk is on (clk is off).  The
dynamic output nodes Y and XY precharge to Vdd-Vt.  Notice the
circuit provides true and complement outputs, the prefix x denoting
the active low signal.

      In evaluation clk is on (xclk is off).  The inputs must be
stable(or originate from another sense amp xor--see explanation
below).  Whenthe clock transitions one side of the xor will
discharge, turning on the opposite p channel device and pulling up
the other output.  Thus one output will go from Vdd-Vt to Gnd, the
other from Vdd-Vt to Vdd.  Since the travel is not full rail (from
Vdd to Gnd) and the P channels are already partially on (Vg=Vdd-Vt)
this transition happens very fast.

      A unique feature of the sense amp circuit is balanced
evaluation trees.  The evaluation trees for both the inverting and
noninverting xor/xnor amp output have an identical topology....