Patent ID: 6181170
Filing Date: 2001-01-30
Classification: H04L

Abstract:
Apparatus for providing a first electrical quantity and a second electrical quantity to an output node in a predetermined relation between said quantities, said apparatus comprising:a first variable resistance;a second variable resistance wherein said first and second variable resistances being serially coupled between a first reference terminal and said output node;a variable current source coupled between said output node and a second reference terminal;a first control means for controlling said first variable resistance to set said first electrical quantity to a first predetermined value when the second electrical quantity has a first predetermined value;a second control means for controlling said second variable resistance to set said first electrical quantity to a second predetermined value when the second electrical quantity has a second predetermined value; anda third control means for controlling said variable current source to set said first electrical quantity to a third predetermined value when the second electrical quantity has a third predetermined value;wherein said first and second variable resistances are first and second transistors, respectively, receiving bias voltages;wherein said variable current source is a third transistor and said first, second and third control means control said first variable resistance, said second variable resistance and said variable current source, respectively, by bias voltages;wherein said first second and third control means each have a control transistor scaled to said first transistor and a control current source scaled to said variable current source, said first control transistor coupled between said first reference terminal and an intermediate node and said control current source coupled between said intermediate node and said second reference terminal; andwherein said first control transistor of said first, second and third control means is coupled to an output of a first operational amplifier with a first input receiving a first reference voltage and a second input at said intermediate node of said first control means.