The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 14, 2001
Filed:
Oct. 28, 1999
John M. Muza, Plano, TX (US);
Texas Instruments Incorporated, Dallas, TX (US);
Abstract
A microphone bias amplifier circuit (,) and method for biasing a microphone with an amplifier circuit. The amplifier circuit (,) has an input stage (,) coupled to an output stage (,). The output stage (,) includes a first transistor (M,) coupled to a feedback loop (,) provides a variable source current (,) to the first transistor (M,) and the output stage output V,. The feedback loop (,) includes an amplifier (,) coupled to the first transistor (M,) and a first current source (I,) conducted through a second transistor (M,) and coupled to the amplifier (,). The amplifier (,) controllably drives a third transistor (M,) coupled to a voltage source (AVDD) to generate the variable current source (I,). The gates of the first (M,) and second (M,) transistors are coupled together and driven by the input stage (,). The third transistor (M,) of the feedback loop (,) provides the variable source current (I,) to the first transistor (M,), whereby the current conducted by the first and second transistors (I,, I,) is equal, and the remainder (I,-I,) of the variable source current (I,) is provided to the load of the output stage (,).