Patent ID: 6016050
Filing Date: 2000-01-18
Classification: G05F

Abstract:
A start-up circuit which provides a fixed bias point suitable for generating fixed bias currents for use in other circuits, comprising:a first transistor connected to receive a start-up signal, said start-up signal having off and on states, and to conduct a first current in response when said start-up signal is in said on state,said first current mirror circuit connected to mirror said first current to produce a first mirrored current,a current sink circuit connected to sink all of said first mirrored current when said first current reaches a predetermined threshold, anda current diversion circuit connected to said start-up signal and arranged to divert from said first transistor a current that varies with the magnitude of the current sunk by said current sink circuit so as to oppose increases in said start-up signal beyond that required to maintain said first current at said predetermined threshold,said first current thereby becoming fixed at said predetermined threshold and providing a fixed bias point that is largely immune to variations in said start-up signal above the level corresponding to said threshold when said start-up signal is in said on state, said fixed bias point suitable for generating fixed bias currents for use in other circuits, said fixed bias point and thereby said fixed bias currents not provided when said start-up signal is in said off state.