Apparatus and method for centrally controlling common mode voltages for a set of receivers
First Claim
1. An apparatus, comprising:
- a differential signal processing circuit comprising;
a first load device, a first input transistor, and a first current source transistor coupled in series between a first upper voltage rail and a lower voltage rail, wherein the first input transistor includes a first gate configured to receive a positive component of an input differential signal and a first drain configured to produce a negative component of an output differential signal; and
a second load device, a second input transistor, and a current control source transistor coupled in series between the first upper voltage rail and the lower voltage rail, wherein the second input transistor includes a second gate configured to receive a negative component of the input differential signal and a second drain configured to produce a positive component of the output differential signal;
a local common mode voltage control circuit configured to receive an external common mode control current and generate therefrom a bias voltage for gates of the first and second current source transistors for setting a common mode voltage of the output differential signal to substantially a target common mode voltage; and
an external common mode voltage control circuit configured to generate the external common mode control current.
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Accused Products
Abstract
A differential signal processing circuit includes a local common mode voltage control circuit for controlling a common mode voltage of an output differential signal generated by the differential signal processing circuit based on an external common mode control current generated by an external common mode voltage control circuit. The differential signal processing circuit, which may be configured as a variable gain amplifier (VGA) or a continuous time linear equalizer (CTLE), includes a pair of load devices, a pair of input transistors, and a pair of current source transistors coupled via separate paths between upper and lower voltage rails. The external control circuit includes a replica circuit including a replica load device, a replica input transistor, and a replica current source transistor. The external control circuit sets the replica common mode voltage to a target using a current, wherein the external common mode control current is based on that current.
19 Citations
25 Claims
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1. An apparatus, comprising:
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a differential signal processing circuit comprising; a first load device, a first input transistor, and a first current source transistor coupled in series between a first upper voltage rail and a lower voltage rail, wherein the first input transistor includes a first gate configured to receive a positive component of an input differential signal and a first drain configured to produce a negative component of an output differential signal; and a second load device, a second input transistor, and a current control source transistor coupled in series between the first upper voltage rail and the lower voltage rail, wherein the second input transistor includes a second gate configured to receive a negative component of the input differential signal and a second drain configured to produce a positive component of the output differential signal; a local common mode voltage control circuit configured to receive an external common mode control current and generate therefrom a bias voltage for gates of the first and second current source transistors for setting a common mode voltage of the output differential signal to substantially a target common mode voltage; and an external common mode voltage control circuit configured to generate the external common mode control current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method, comprising:
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generating an output differential signal based on an input differential signal; receiving an external common mode voltage control current; controlling a common mode voltage of the output differential signal based on the external common mode control current; and generating the external common mode control current, wherein generating the external common mode control current comprises; generating a replica common mode voltage related to the common mode voltage of the output differential signal; generating a target common mode voltage; controlling the replica common mode voltage so that the replica common mode voltage is substantially the same as the target common mode voltage; and generating the external common mode control current based on controlling the replica common mode voltage. - View Dependent Claims (21, 22)
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23. An apparatus, comprising:
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means for generating an output differential signal based on an input differential signal; means for receiving an external common mode voltage control current; and means for controlling a common mode voltage of the output differential signal based on the external common mode control current; and means for generating the external common mode control current, wherein the means for generating the external common mode control current comprises; means for generating a replica common mode voltage related to the common mode voltage of the output differential signal; means for generating a target common mode voltage; means for controlling the replica common mode voltage so that the replica common mode voltage is substantially the same as the target common mode voltage; and means for generating the external common mode control current based on controlling the replica common mode voltage. - View Dependent Claims (24, 25)
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Specification