Digitally programmable capacitor array

US7245519B2 · kind B2 · utility

Assignee

• Freeescale Semiconductor, Inc. · US

Inventors

• Dale J. McQuirk · Austin, US
• Michael T. Berens · Austin, US

Key dates

• Filing date: Aug 22, 2005
• Grant date: Jul 17, 2007
• Expiry date: Dec 23, 2025

Classification

• Technology area (CPC H): Electricity
• CPC primary: H03J2200/10

Abstract

A programmable capacitor array does not require separate switching transistors because the capacitors themselves have a switchable capacitance, which capacitors are made in the manner of regular N channel transistors with their source/drains connected to each other. When a logic low is applied to the gate, the capacitance is relatively low and the capacitance is what is commonly called parasitic capacitance. The capacitance increases significantly when a logic high is applied to the gate because the logic high has the effect of inverting the channel. Thus, the capacitor array is made of transistors that themselves have switchable capacitance operated so that no separate switching transistors are required. This allows for construction of an array of unit capacitors to achieve monotonic operation and good linearity using conventional manufacturing of N channel transistors while achieving significant area savings and reduced power consumption.