Patent ID: 6011432
Filing Date: 2000-01-04
Classification: H03H

Abstract:
An integrated circuit comprising one or more DC-isolated variable capacitors, wherein each variable capacitor comprises three capacitive elements configured in a T-structure, wherein:a first capacitive element is connected between an input node of the variable capacitor and a common node of the variable capacitor;a second capacitive element is connected between the common node and a reference node of the variable capacitor;a third capacitive element is connected between the common node and an output node of the variable capacitor;the second capacitive element comprises:(a) a buffer amplifier connected between a control signal node of the variable capacitor and the common node; and(b) an active device connected between the common node and the reference node, wherein:the active device has a capacitance that is dependent on a voltage level of the common node; andwhen a control signal is applied to the control signal node, the buffer amplifier generates and applies a buffered control signal to the common node to control the capacitance of the active device, thereby adjusting the capacitance of the DC-isolated variable capacitor.