Patent ID: 7898295
Filing Date: 2011-03-01
Classification: H03K

Abstract:
1. An apparatus for differential signaling, the apparatus comprising: a replica bias circuit comprising a replica NMOS transistor and a replica PMOS transistor; an explicit resistor having a resistance of about N times a characteristic impedance intended to be driven by a main driver circuit, wherein the explicit resistor is operatively coupled in a current path between sources of the replica NMOS transistor and the replica PMOS transistor, wherein N is greater than 1; the main driver circuit comprising a driver NMOS transistor and a driver PMOS transistor and steering switches; a biasing circuit configured to bias the replica NMOS transistor such that the source of the replica NMOS transistor is biased relative to a first reference level V a protection control circuit and protection switches, wherein the protection control circuit is configured to control the protection switches, wherein in a normal operating mode, the protection switches permit the biasing circuit to bias the driver NMOS transistor and the driver PMOS transistor, and wherein in a protected mode of operation, the protection switches cut off the driver NMOS transistor and the driver PMOS transistor.