Patent ID: 7109781
Filing Date: 2006-09-19
Classification: H01F,H01L,H03B,H03D,H03F,H03G,H03H,H03J,H03L

Abstract:
1. An apparatus for controlling temperature induced quality (Q) variation in an integrated circuit filter, the integrated circuit filter including a filter element having a series resistance that varies proportionally with a temperature of the filter element, comprising: an amplifier having a positive input terminal, a negative input terminal, and an output terminal; a first variable resistor coupled in series with the filter element and having a control terminal coupled to the output of the amplifier; a second variable resistor having a first terminal, a second terminal, and a control terminal, wherein the control terminal of the second variable resistor is coupled to the output terminal of the amplifier; a resistor coupled in series between the negative input terminal of the amplifier and the first terminal of the second variable resistor; and a dummy filter element coupled in series between the positive input terminal of the amplifier and the second terminal of the second variable resistor.