Patent ID: 6166587
Filing Date: 2000-12-26
Classification: G05F,H03L

Abstract:
CMOS circuit for generating a current reference, comprising at least a first unit (G1) destined to generate a first current reference and comprising:a first and a second element (S1, S2) having respective current-voltage characteristics with such a behaviour as to present an intersection point whereto corresponds said first current reference (I1), both elements being made by active components and the first element (S1) comprising a first transistor (T1) at whose output the first reference (I1) is present,means (SP) for injecting a same current into said two elements (S1, S2),a start up circuit (SU), to bring the unit to operate in correspondence with said intersection point of the current-voltage characteristics of said two elements (S1, S2), anda feedback circuit (AD) to maintain the working point of the circuit in correspondence with said intersection point as the operating conditions vary,characterised in thatsaid first transistor (T1) is a low gain transistor,said second element (S2) comprises a second and a third transistors (T2, T3) connected in series, which have the same type of doping as the first transistor (T1) and present much higher gain than the first transistor (T1);the injection means (SP) are arranged to inject such a current as to bring the first transistor (T1) to operate in conditions of strong saturation and the second and third transistors (T2, T3) to operate in conditions of weak inversion, andthe feedback circuit comprises a differential amplifier (AD) that receives at its inputs the voltage present across said first and second element (S1, S2) and provides said injection means (SP), with a control signal such as to maintain the circuit in said working point.