Programmable gain amplifier for use in data network

• US 6,424,221 B1
• Filed: 01/25/2001
• Issued: 07/23/2002
• Est. Priority Date: 06/19/2000
• Status: Expired due to Term

• Current Assignee: Globalfoundries US Incorporated (GlobalFoundries, Inc.)
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Korn, Thomas
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Choe, Henry
• Application Number:
  US09/770,065
• Publication Number:
  US 20020024385A1
• Time in Patent Office: 544 Days
• Field of Search: 330/86, 330/282, 330/144, 330/284
• US Class Current: 330/282
• CPC Class Codes: H03M 1/183 the feedback signal controlling the gain of an amplifier or attenuator preceding the analogue/digital converter

Abstract

A data networking device having a variable gain amplifier with a first selectable impedance and a second selectable impedance for adjusting gain of the variable gain amplifier. The data networking device has an analog to digital converter for converting an analog output signal of the variable gain amplifier to a digital signal. The data networking device has a digital signal monitoring circuit for monitoring the digital signal and supplying feedback signals to actuate the first and second selectable impedances as a function of the digital signal, thereby adjusting the gain of the variable gain amplifier. A method of controlling a variable gain amplifier is also disclosed. An analog output signal of the variable gain amplifier is converted to a digital signal by an analog to digital converter. The method includes determining a portion of dynamic range of the analog to digital converter being used to convert the analog output signal of the variable gain amplifier. The method includes providing a first feedback signal to a first selectable impedance and providing a second feedback signal to a second selectable impedance, the first and second feedback signals adjusting the gain of the variable gain amplifier to increase the dynamic range used by the analog to digital converter.

Claims

1. A data networking device, comprising:

a variable gain amplifier having a first selectable impedance and a second selectable impedance for adjusting gain of the variable gain amplifier;

an analog to digital converter for converting an analog output signal of the variable gain amplifier to a digital signal; and

a digital signal monitoring circuit for monitoring the digital signal and supplying feedback signals to actuate the first and second selectable impedances as a function of the digital signal, thereby adjusting the gain of the variable gain amplifier and wherein the digital monitoring circuit monitors the digital signal to determine the percentage of dynamic range of the analog to digital converter being used to convert the analog output signal of the variable gain amplifier.

2. The data networking device according to claim 1, wherein the first and second selectable impedances each have a resistor ladder and a multiplexer, the multiplexer tapping the resistor ladder based on the feedback signals.

3. The data networking device according to claim 2, wherein the multiplexer is implemented with MOS transistors and the feedback signals are digital select lines for actuating the multiplexers.

4. The data networking device according to claim 1, wherein the variable gain amplifier is provided with a capacitive compensation circuit for adjusting the bandwidth of the variable gain amplifier.

5. The data networking device according to claim 4, wherein the capacitive compensation circuit has a plurality of capacitors one of which being coupled to a compensation node of the variable gain amplifier with a multiplexer.

6. The data networking device according to claim 1, wherein the percentage of dynamic range is a function of the average signal value of the digital signal for a predetermined period of time.

7. The data networking device according to claim 1, wherein a signal modulation type is determined by a modulation detection and feedback circuit, the modulation detection and feedback circuit producing a modulation type gain feedback signal which is factored into the feedback signals to actuate the first and second selectable impedances.

8. The data networking device according to claim 1, wherein the variable gain amplifier is a current feedback operational amplifier.

9. The data network device according to claim 1, wherein the first selectable impedance has a resistor ladder having a first terminal connected to receive an analog voltage signal and a second terminal connected to a voltage reference, and a multiplexer for coupling an output of the first selectable impedance to a selected point on the resistor ladder, the output connected to a first input of an amplifier component, the feedback signals actuating the multiplexer to select a portion of the resistor ladder to be connected between the first terminal and the first amplifier input.

10. The data network device according to claim 1, wherein the second selectable impedance has a resistor ladder having a first terminal connected to an input of an amplifier component and a second terminal connected to a voltage reference, and a multiplexer for coupling the first terminal to a selected point on the resistor ladder, the feedback signals actuating the multiplexer to select a portion of the resistor ladder to be connected between the input of the amplifier component and the voltage reference.

11. The data network device according to claim 10, wherein the amplifier component has a feedback impedance connected between an output of the amplifier component and the input of the amplifier component.

12. The data network device according to claim 9, wherein the second selectable impedance has a resistor ladder having a first terminal connected to a second input of an amplifier component and a second terminal connected to a voltage reference, and a multiplexer for coupling the first terminal to a selected point on the resistor ladder, the feedback signal actuating the multiplexer to select a portion of the resistor ladder to be connected between the second input of the amplifier component and the voltage reference.

13. The data network device according to claim 12, wherein the amplifier component has a feedback impedance connected between an output of the amplifier component and the second input of the amplifier component.

14. A method of controlling a variable gain amplifier, an analog output signal of the variable gain amplifier being converted to a digital signal by an analog to digital converter, comprising the steps of:

determining a portion of dynamic range of the analog to digital converter being used to convert the analog output signal of the variable gain amplifier; and

providing a first feedback signal to a first selectable impedance and providing a second feedback signal to a second selectable impedance, the first and second feedback signals adjusting the gain of the variable gain amplifier to increase the dynamic range used by the analog to digital converter.

15. The method according to claim 14, wherein the portion of dynamic range used by the analog to digital converter is a function of the average signal value of the digital signal for a predetermined period of time.

16. The method according to claim 14, further comprising the step of selectively coupling a first input of an amplifier component of the variable gain amplifier to an input voltage signal through a portion of a resistor ladder in accordance with the first feedback signal.

17. The method according to claim 14, further comprising the step of selectively coupling a second input of an amplifier component of the variable gain amplifier to a voltage reference through a portion of a resistor ladder in accordance with the second feedback signal.

18. The method according to claim 16, further comprising the step of selectively coupling a second input of an amplifier component of the variable gain amplifier to a voltage reference through a portion of a resistor ladder in accordance with the second feedback signal.

19. The method according to claim 14, further comprising the steps of determining a modulation type of a receive signal, producing a modulation type gain feedback signal and factoring the modulation type gain feedback signal into the first and second feedback signals.

20. The method according to claim 14, wherein the first and second feedback signals are digital select signals for controlling multiplexers in the first and second selectable impedances.

21. The method according to claim 14, further comprising the steps of determining a bandwidth of a receive signal and providing a feedback signal to a couple one of a series of compensation capacitors to a compensation node of the variable gain amplifier.