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Offset cancellation for continuous-time circuits

a continuous-time circuit and offset cancellation technology, applied in the field of electric circuits, can solve problems such as imposing losses on the signal being transmitted, and achieve the effect of greater stability

Active Publication Date: 2012-05-24
ALTERA CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The proposed solution improves the stability and offset cancellation ability of the circuit, allowing for greater tolerance to open-loop phase shifts and time delays, while maintaining a similar filter size, and reduces the detrimental effects of process, voltage, and temperature variations on stability.

Problems solved by technology

The medium that conveys the signal from the transmitter to the receiver usually imposes losses on the signal being transmitted.

Method used

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  • Offset cancellation for continuous-time circuits
  • Offset cancellation for continuous-time circuits
  • Offset cancellation for continuous-time circuits

Examples

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Embodiment Construction

[0023]For the purposes of discussion and not limitation, it is generally assumed that the cascaded circuits described below receive (and output) data signals that are differential signals. However, it should be appreciated that principles of the presently-disclosed invention may also apply to single-ended signals.

[0024]Conventional continuous-time cascaded circuits typically employ a feedback loop that filters an output offset voltage, pass it though a high-gain amplifier, and apply a feedback current to the first stage of the circuit to reduce the offset in a continuous time manner. Such a conventional continuous-time cascaded circuit with a feedback loop is shown in FIG. 1. Note that continuous-time circuits operate on continuous-time signals, as opposed to sampled discrete-time signals.

[0025]In the example circuit 100 shown in FIG. 1, four equalizer stages (Eq1, Eq2, Eq3, and Eq4) are cascaded in a serial chain. The first equalizer stage (Eq1) has an input load (RL) and receives ...

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Abstract

One embodiment relates to a continuous-time circuit configured with an offset cancellation loop. The continuous-time circuit includes a multi-stage amplifier chain, including a first amplifier stage and a last amplifier stage, and an offset cancellation loop. The offset cancellation loop is configured to receive an output of the last amplifier stage and to provide an offset correction voltage signal to the first amplifier stage. The offset compensation loop may create one dominant pole and a single consequential parasitic pole so as to have greater stability and may advantageously achieve a second-order roll-off in response magnitude at higher frequencies. Other embodiments, aspects, and features are also disclosed.

Description

BACKGROUND[0001]1. Technical Field[0002]The present invention relates generally to electrical circuits. More particularly, the present invention relates to offset cancellation for continuous-time circuits.[0003]2. Description of the Background Art[0004]A high speed serial interface (“HSSI”) may be used to communicate between devices in a system. Typically, it is the intention for the transmitter in such a system to transmit a digital (binary) signal having two distinctive levels, and well-defined (i.e., very steep) transitions from either of these levels to the other level. Such steep transitions are essential to transmitting data at high speed. The medium that conveys the signal from the transmitter to the receiver usually imposes losses on the signal being transmitted. These losses generally include diminished signal amplitude and reduced transition steepness.[0005]To maintain accurate, high-speed data transmission, it is necessary for the circuitry to compensate for these losses....

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H03F3/45H03F1/00
CPCH03F1/30H03F3/45197H03F3/45973H03F2203/45374H03F2200/405H03F2203/45354H03F2200/375
Inventor NARAYAN, SRIRAMSU, XIAOYANSHUMARAYEV, SERGEY
Owner ALTERA CORP