Patent ID: 6452458
Filing Date: 2002-09-17
Classification: H03K,H03L

Abstract:
A voltage-controlled oscillator, comprising:a ring oscillator including a plurality of differential amplifiers each having a first input terminal, a second input terminal, a first output terminal, a second output terminal and a current limiting terminal, said first and second input terminals of the plurality of said differential amplifiers and said first and second output terminals of said differential amplifiers corresponding thereto being ring-connected, each said differential amplifier comprising a first load circuit connected to said first output terminal thereof and a second load circuit connected to said second output terminal thereof, said first and second load circuits operating always in a linear operating region, wherein each said differential amplifier includes: a first transistor connected between a first power source line and a first node and having a gate supplied with a current control voltage, a second transistor connected between said first node and said first output terminal thereof and having a gate supplied with a first input signal, a third transistor connected between said first node and said second output terminal thereof and having a gate supplied with a second input signal, wherein said first load circuit is connected between said first output terminal and a second power source line and said second load circuit connected between said second output terminal and said second power source line, and wherein said first load circuit includes: a fourth transistor connected between said first output terminal thereof and said second power source line and having a gate supplied with a first load control voltage, and a fifth transistor connected between said first output terminal thereof and said second power source line and having a gate supplied with a second load control voltage, and wherein said second load circuit includes: a sixth transistor connected between said second output terminal thereof and said second power source line and having a gate supplied with the first load control voltage, and a seventh transistor connected between said second output terminal thereof and said second power source line and having a gate supplied with the second load control voltage.