Patent ID: 6356141
Filing Date: 2002-03-12
Classification: G05F,H03F,H04L

Abstract:
A constant-current output circuit for outputting a constant current to a cable coupled to a bias voltage through a terminating resistor, said constant-current output circuit comprising:a drive transistor having a gate electrode, a source electrode coupled to a power supply, and a drain electrode coupled to said cable; and adjustment means for adjusting the current drive capability of said drive transistor so that when a voltage between said drain electrode and said source electrode undergoes a variation due to a change in said bias voltage, a variation in drain current of said drive transistor accompanied by said drain-source voltage variation is compensated such that said drain current of said drive transistor is maintained at a substantially same level so as to generate said constant current, wherein said adjustment means has a function of adjusting, based on system information indicative of a prediction of the change in said bias voltage, the current drive capability of said drive transistor.