Logarithmic taper resistor with zero crossing changes

• US 5,923,159 A
• Filed: 03/11/1997
• Issued: 07/13/1999
• Est. Priority Date: 06/30/1995
• Status: Expired due to Term

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Dallas Semiconductor Corporation (Analog Devices, Inc.)
• Inventors: Ezell, Richard William
• Primary Examiner(s): Hecker, Stuart N.
• Application Number:
  US08/815,503
• Time in Patent Office: 854 Days
• Field of Search: 323/354, 338/89, 338/200, 338/201, 327/536
• US Class Current: 323/354
• CPC Class Codes: G05B 24/02 electric
• CPC Class Codes: H03M 1/664 Non-linear conversion not otherwise provided for in subgroups of H03M1/66
• CPC Class Codes: H03M 1/765 using a single level of switches which are controlled by unary decoded digital signals

Abstract

A digital potentiometer capable of being connected directly to an electronic switch is disclosed. The digital potentiometer for example may utilize a 64 step resistor array, which would then have 64 steps. Each of the steps have precise values so as to accurately attenuate a signal in logarithmic steps. The logarithmic resistor is connected to a gate device which in turn has a voltage source connected to it designed to provide the threshold or turn-on voltage for the device for each of the 64 steps and wiper points of the resistor array.

Claims

1. A semi-conductor potentiometer which comprises:

a resistor array comprised of a plurality of cells of resistors each having a resistive value wherein the arrangement of resistors and resistive value of the resistors varies from cell to cell;

a plurality of gate devices for selecting a wiper point wherein there exists a wiper point for every cell and there exists a gate device for every wiper point adapted for selecting said wiper point;

a multiplex control device which comprises a zero-crossing detector adapted for triggering potentiometer changes at or near a zero-crossing of a signal being amplified; and

an interface device connected to the multiplexer control device adapted for interfacing said multiplex control device directly to an external switch without requiring a special circuit or CPU to provide an interface.

2. In an amplifier for amplifying a signal, a potentiometer comprising:

a resistor array comprised of a plurality of cells of resistors, each of said plurality of cells of resistors having a total resistive value;

a plurality of wiper points for separating each of said plurality of cells of resistors;

means for selecting at least one of said plurality of wiper points;

triggering means for triggering potentiometer changes at or near a zero-crossing of the signal being amplified; and

an interface means connected to said triggering means, said interface means for interfacing said triggering means to an external switch.

3. The potentiometer as recited in claim 2, wherein said resistors and said total resistive value of each said plurality of cells of resistors varies from cell to cell.

4. The potentiometer as recited in claim 2, wherein said selecting means includes a plurality of gate devices.

5. The potentiometer as recited in claim 2, wherein said triggering means includes a zero-crossing detector.

6. The potentiometer as recited in claim 2, wherein said triggering means includes a multiplex control device.

7. In a system for amplifying a signal, a potentiometer comprising:

a plurality of cells of resistors, each of said plurality of cells of resistors having a total resistive value;

a plurality of wiper points, wherein each of said plurality of cells of resistors are connected by at least one of said plurality of wiper points;

a plurality of gate devices for selecting at least one of said plurality of wiper points;

a control for triggering potentiometer changes at or near a zero-crossing of the signal being amplified; and

an interface connected to the control device.

8. The potentiometer as recited in claim 7, wherein said total resistive value of each of said plurality of cells of resistors varies from cell to cell.

9. The potentiometer as recited in claim 7, wherein said control includes a zero-crossing detector.

10. The potentiometer as recited in claim 7, wherein said interface includes an external switch.