Importance

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Abstract

Disclosed are solid-state potentiometers having high resolution and high accuracy. An exemplary potentiometer comprises a first main terminal, a second main terminal, a wiper terminal, and a resistor stack comprising a plurality M of resistors coupled in series to one another at a plurality of M-1 internal nodes. Each of the resistors in the stack has substantially the same value of R.sub.S ohms. The potentiometer further comprises a first variable resistance network coupled between one end of the resistor stack and the potentiometer's first main terminal, and a second variable resistance network coupled between the other end of the resistor stack and the potentiometer's second main terminal. The first variable resistance network has a variable resistance value R.sub.1 which varies between zero ohms and R.sub.P ohms. The second variable resistance network has a variable resistance value R.sub.2 which is maintained substantially at value of (R.sub.P -R.sub.1). The wiper terminal is selectively coupled to one of the internal nodes of the resistor stack, or to one of the ends of the resistor stack, to provide a coarse setting of the potentiometer's wiper position. The resistances of the variable resistance networks are changed to provide the fine resolution for the potentiometer's wiper position. The present invention provides a large number of discrete wiper positions with a constant end-to-end resistance, while using a small number of resistors and transistors relative to prior art implementations. A further advantage of the invention is that the potentiometer may be constructed with a small number of selection transistors turned on within the current path between the potentiometer's main terminals, thereby providing higher accuracy.

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First Claim