Patent ID: 6512393
Filing Date: 2003-01-28
Classification: H04L

Abstract:
An active termination circuit for terminating a signal traversing on a transmission line of an electronic device, comprising:a bottom clamping transistor coupled to a first potential having a bottom clamping transistor control node arranged for clamping said signal at about a first reference voltage; a bottom threshold reference transistor coupled to a first reference voltage supply configured to supply the first reference voltage, wherein the bottom threshold reference transistor provides a first bias voltage to said bottom clamping transistor control node that biases said bottom clamping transistor control node at about a first threshold voltage above said first reference voltage, said first threshold voltage representing a threshold voltage of said bottom clamping transistor; a top clamping transistor coupled to a second potential having a top clamping transistor control node arranged for clamping said signal at about a second reference voltage; a top threshold reference transistor coupled to a second reference voltage supply configured to supply the second reference voltage, wherein said top threshold reference transistor provides a second bias voltage to said top clamping transistor control node that biases said top clamping transistor control node at about a second threshold voltage below said second reference voltage, said second threshold voltage representing a top clamping transistor threshold voltage; and a variable current supply coupled to the bottom threshold transistor and the top threshold transistor arranged to supply a first bias current to the bottom threshold transistor and a second bias current to the top threshold transistor based upon said signal, wherein the variable current supply includes, a first current source arranged to provide a first bias current to the bottom threshold reference transistor based upon the signal, and a second current source arranged to provide a second bias current to the top threshold reference transistor based upon the signal, wherein the first current source and the second current source are anti-phase to each other so as to reduce the average DC power dissipation of the circuit.