Single-ended-to-differential converter with common-mode voltage control

• US 6,873,210 B2
• Filed: 03/04/2004
• Issued: 03/29/2005
• Est. Priority Date: 03/26/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Mulder, Jan, Lin, Chi-Hung, Lugthart, Marcel
• Primary Examiner(s): Shingleton, Michael B.
• Application Number:
  US10/791,878
• Publication Number:
  US 20040164770A1
• Time in Patent Office: 390 Days
• Field of Search: 330/258, 330/117, 330/301, 330/307, 330/284, 327/307, 327/346
• US Class Current: 330/258
• CPC Class Codes: H03H 11/32 Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns

Abstract

Provided is a circuit to perform single-ended to differential conversion while providing common-mode voltage control. The circuit includes a converter to convert a single-ended signal to a differential signal and a stabilizing circuit adapted to receive the differential signal. The stabilizing circuit includes a sensor configured to sense a common-mode voltage level of the differential signal and a comparator having an output port coupled to the converter. The comparator is configured to compare the differential signal common-mode voltage level with a reference signal common-mode voltage level and produce an adjusting signal based upon the comparison. The adjusting signal is applied to the converter via the output port and is operative to adjust a subsequent common-mode voltage level of the differential signal.

Claims

1. A method to convert a single-ended signal to a differential signal, comprising:

attenuating a single-ended signal received within an attenuator and producing a differential signal at differential output ports formed within the attenuator, the differential signal being based upon the attenuated single-ended signal and a received DC signal;

detecting a common-mode voltage level of the differential signal and providing the detected common-mode voltage level to an inverting input port of an amplifier;

providing a reference common-mode voltage signal to a non-inverting input port of the amplifier;

comparing the detected common-mode voltage level with a voltage level of the reference signal and providing an adjusting signal at an amplifier output port based upon the comparison; and

adjusting common-mode voltage levels of subsequently produced differential signals based upon the adjusting signal.

2. The method of claim 1, wherein an adjusted common-mode voltage level is substantially equal to the voltage level of the reference signal.

3. An apparatus for converting a single-ended signal to a differential signal, comprising:

means for attenuating a single-ended signal received within an attenuator and producing a differential signal at differential output ports formed within the attenuator, the differential signal being based upon the attenuated single-ended signal and a received DC signal;

means for detecting a common-mode voltage level of the differential signal and providing the detected common-mode voltage level to an inverting input port of an amplifier;

means for providing a reference common-mode voltage signal to a non-inverting input port of the amplifier;

means for comparing the detected common-mode voltage level with a voltage level of the reference signal and providing an adjusting signal at an amplifier output port based upon the comparison; and

means for adjusting common-mode voltage levels of subsequently produced differential signals based upon the adjusting signal.

4. The apparatus of claim 3, wherein an adjusted common-mode voltage level is substantially equal to the voltage level of the reference signal.