Patent ID: 7256660
Filing Date: 2007-08-14
Classification: H03B

Abstract:
1. A CMOS LC_TANK oscillator comprising: a pair of symmetric inductors; and a differential pair of transistors, wherein said inductors have a first one of their terminals interconnected at a supply node to which a voltage supply is applied through a supply resistor and a second terminal connected to the drain of a respective one of said transistors, said transistors having their sources interconnected at a tail node which is connected to ground through a tail resistor, and further comprising a current control loop for controlling a core current between said top and tail nodes so as to keep a voltage drop across said tail resistor at a level determined by a reference voltage; wherein said current control loop includes a current control transistor that has a current path connected between the supply node and ground, an operational amplifier with a first input connected to the reference voltage, a second input connected to said tail node and an output connected to the gate of said current control transistor.