KR101470578B1 - Light receiver - Google Patents

Abstract

A light receiver includes an automated boundary controller which outputs reference voltage; an on-chip regulator which generates on-chip voltage which is lower than external voltage; a preamplifier unit which is operated in a single mode, receives current signals from a light detector, changes/amplifies the current signals into voltage signals by receiving the on-chip voltage from the on-chip regulator, and outputs the voltage signals in which power voltage noise is minimized; and a noise cancelation block which receives the reference voltage outputted from the automated boundary controller and common mode voltage outputted from the preamplifier, adds the same with the on-chip voltage, and outputs the same to the preamplifier.

Description

[0001] DESCRIPTION [0002] LIGHT RECEIVER [

The present invention relates to a light receiving apparatus for improving noise characteristics.

The optical receiver determines the optical transmission distance, optical link system budget, etc. as a core block of the optical interconnect system. In recent years, demand for improving the performance of the optical receiver has been actively increased with the introduction of silicon-based photodiodes having relatively low performance.

Conventional optical receiver structures have suffered from other performance degradations to improve noise characteristics. In the past, the adoption of a compound semiconductor-based high-performance photo-detectors made it possible to use such a light receiving circuit. However, as the cost competitiveness of optical transmission systems has recently become an issue, it is essential to improve the performance of the optical receiver circuit in a situation where the use of cheap optical detectors is becoming active.

In a conventional optical receiving apparatus, a Pseudo Differential Amplification (PEM) scheme is mainly used to improve common-mode noise characteristics. That is, by using a differential amplifier, efforts have been made to eliminate common mode noise caused by power-supply noise and ground bouncing phenomenon. A differential amplifier is basically effective at removing common mode noise by amplifying the difference of a high-speed signal with a phase difference of 180 degrees.

However, the optical receiving apparatus is essentially a single mode in which only one input is input, and a conversion into a differential mode is required, and a DC offset error occurs in the process. Therefore, an additional block is needed to compensate for this.

Also, due to the same reason, the optical receiving system using the differential amplifier always has a loss of 6 dB in the transimpedance gain compared with the case of using the single mode amplifier. Additional blocks are needed to compensate for these losses, and the power consumption is also very high.

In order to solve such a problem, optical receiving methods using a single mode amplifier have been proposed. Single-mode amplifiers are vulnerable to common mode noise, but have the advantage of low power consumption and no need for additional blocks. However, even if a single-mode amplifier is used, an additional block for converting from a single mode to a differential mode is required because a postamplifier (PoA) having a large signal size must operate in a differential mode. An offset error occurs.

In addition, it is common to further insert an on-chip regulator circuit to solve the common mode noise problem. The on-chip regulator is an attempt to minimize supply-voltage noise, which accounts for the largest portion of the common-mode noise. However, the common-mode noise characteristic has a significantly lower performance than the differential mode, despite the use of an on-chip regulator.

However, differential mode amplifiers have problems such as large power consumption and offset errors, and single mode amplifiers suffer from large common mode noise and offset errors.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a noise canceling block (NCB) and a feedforward automatic threshold control (ATC) to a single mode optical receiver equipped with an on-chip regulator, And to provide a light receiving device that minimizes noise and offset errors.

According to one aspect of the present invention, an optical receiver apparatus includes an automatic boundary point controller for outputting a reference voltage, an on-chip regulator for generating an on-chip voltage lower than the external voltage from an external voltage, A preamplifier for receiving the on-chip voltage from the on-chip regulator and converting and amplifying the current signal into a voltage signal to output the voltage signal with minimized power supply voltage noise, And a noise cancellation block for receiving the common mode voltage output from the preamplifier, adding the sum to the on-chip voltage, and outputting the sum to the preamplifier.

And a post-amplification unit operating in a differential mode and disposed at a rear stage of the pre-amplification unit,

Wherein the automatic boundary point controller comprises:

And a feedforward structure for normalizing the reference voltage and outputting it as a reference voltage of the postamplifier.

And a single-to-differential conversion unit that connects the pre-amplifier unit and the post-amplifier unit and includes the automatic boundary point controller.

And a low-pass filter for removing an offset error of the post-amplifier unit.

The post-

Three-stage high-speed amplifier or four-stage high-speed amplifier.

And a driving unit for driving a transmission line or an input capacitance of the output stage.

And an equalizer including a high-pass filter that is inverse to the transfer function of the low-pass filter.

And a peripheral device portion including a band cap reference and a property circuit and providing a bias current and a reference voltage.

According to the embodiment of the present invention, a noise canceling block for improving noise characteristics and a feedforward automatic boundary point control block for offset error improvement are employed, and a power consumption is improved by adopting a single mode amplifier and an on- It is possible to improve the noise characteristic of the optical receiver without increasing the offset error, and to greatly reduce the offset error. In addition, through such a configuration, it is possible to realize a light transmission system without lowering the performance even if a low-priced silicon-based light detector is used, and it is possible to realize an ultra low power type optical transmission and reception system which is a recent issue.

1 shows a light receiving apparatus according to an embodiment of the present invention.
2 is a diagram for comparing the configurations of a conventional preamplifier and a preamplifier according to an embodiment of the present invention.
3 (a) shows a conventional ATC configuration, and FIG. 3 (b) shows a configuration of an ATC according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise.

Hereinafter, a light receiving apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

1 shows a light receiving apparatus according to an embodiment of the present invention.

1, the optical receiver includes a preamplifier (PrA) 200 for converting a fine current signal input from a photodetector (PD) 100 into a voltage signal and amplifying the voltage signal .

The preamplifier (PrA) 200 is located at the front end of a light receiving device, which is a cascade system, and is a very important block for determining the overall noise performance.

The output voltage of the regulator 300 is input to the preamplifier 200 in conjunction with the output voltage of the Noise Canceling Block (NCB)

At this time, the regulator 300 is an on-chip regulator designed to generate an on-chip voltage VDDreg lower than the external voltage VDD from the external voltage VDD. At this time, not only a low voltage but also an on-chip voltage with improved regulated quality is generated.

Here, the noise canceling block 400 includes an amplifier 401 and an adder 403. The amplifier 401 receives a reference voltage from a feed-forward Automatic Threshold Control (ATC) 501 and receives a common-mode voltage output from the pre-amplifier unit 200. As described above, the amplifier 401 feeds back the common mode voltage output from the preamplifier unit 200.

The adder 403 adds the output voltage output from the regulator 300 and the voltage output from the amplifier 401 and inputs the result to the preamplifier unit PrA. The adder 403 removes the common mode voltage noise from the output voltage of the regulator 300. Accordingly, the output voltage output from the regulator 300, from which the noise of the common mode voltage is removed, is input to the pre-amplifier unit 200.

Since the preamplifier 200 operating in the single mode is very vulnerable to power supply voltage noise, the regulator 300 minimizes power supply voltage noise. The noise cancellation block 400 receives the reference voltage from the feed-forward ATC 501 and feeds it back to the preamplifier unit 200 in conjunction with the common mode voltage output from the preamplifier unit 200, The output voltage of the regulator 300 is controlled to improve the noise characteristic.

The single-differential converter 500 includes a pre-amplifier unit 200 including a feed-forward ATC 501 and operating in a single mode and a post amplifier (PoA) 600 operating in a differential mode ). The offset error generated in this process also has a great influence on the overall noise performance, and the offset error can be minimized by using the feedforward type ATC instead of the conventional feedback type ATC. In the conventional feedback method, a signal of a differential node (ie, a node operating in a differential mode) is fed back to a cross through a low-pass filter so as to minimize an offset error, . Meanwhile, the feedforward method according to the present invention is a method of detecting a swing in a differential amplifier 600, which operates in a differential mode, that is, a differential mode, and selecting an intermediate value thereof in real time to eliminate an offset error.

Since the feed-forward ATC 501 may cause signal distortion and jitter and signal loss during the process of applying the signal output from the preamplifier 200 to the postamplifier 600, a reference level . That is, the maximum value and the minimum value of the input signal are detected, and the DC value as the intermediate value is output.

The amplifier 503 amplifies the difference between the value (DC value) output from the feed-forward ATC 501 and the input signal, and transmits the amplified difference to the post-amplifier unit 600.

On the other hand, a post amplifier (PoA) 600 amplifies the output value of the amplifier 503. At this time, the output amplitude is always constant regardless of the input value.

The post-amplifier unit 600 should exhibit a large voltage gain characteristic for a sufficient output voltage. The post-amplifier unit 600 may be composed of three or four stages of high-speed amplifiers. The post-amplifier unit 600 is connected to a low-pass filter (LPF) The low-pass filter 700 minimizes a high voltage gain, that is, an offset error that may occur due to the post-amplifier unit 600. [ That is, the DC value of each differential node, that is, the post-amplifier unit 600 can be detected through the low-pass filter 700, and the offset error is eliminated by cross-feeding the DC value.

The driving unit 800 includes an equalizer 801 and a driving unit 803.

The equalizer 801 is a component that can be added or removed depending on the operation speed of the light receiving device. The equalizer 801 has a form of a high-pass filter which is opposite to the transfer function of the low-pass filter type of the light receiving device.

The driver 803 consumes a large current to drive the input capacitance of a clock-data reconstructor (not shown), which is the output line or the next block. Here, a clock-data reconstructor (not shown) is generally used behind the optical receiver, but a description thereof will be omitted regardless of the embodiment of the present invention.

Also, by using a good reference voltage output from the regulator 300 as the power supply voltage, the noise characteristics of the blocks 200 to 800 can be improved.

The peripheral unit 900 includes a Bandgap Reference (BGR) 901 and a Proportional To Absolute Temperature (PTAT) circuit 903. This peripheral unit 900 provides the bias current and the reference voltage of the regulator 300 and all blocks of the optical receiver.

2 is a diagram for comparing the configurations of a conventional preamplifier and a preamplifier according to an embodiment of the present invention.

2 (a), the conventional preamplifier unit uses the output voltage of the regulator as the power supply voltage as it is.

2B, the preamplifier 200 according to the embodiment of the present invention includes a noise canceling block 400 for detecting an output of the regulator 300, an output of the preamplifier 200, an ATC And receives the output of the power amplifier 501 as an input, and uses the feedback output from which the common mode noise is removed as the power supply voltage.

3 (a) shows a conventional ATC configuration, and FIG. 3 (b) shows a configuration of an ATC according to an embodiment of the present invention.

First, referring to FIG. 3 (a), the conventional ATC is a feedback structure. That is, the conventional ATC receives a signal at the output terminal of the amplifier, converts the signals into differential-to-single signals, and passes the low pass filter to automatically find a threshold value.

On the other hand, referring to FIG. 3 (b), the ATC according to the embodiment of the present invention is a feed-forward structure. That is, the ATC 501 is configured to minimize the offset error by obtaining the DC value of the input signal, normalizing the DC value, and utilizing the DC value as a reference voltage of the differential amplifier 600 that is to be provided at the next stage.

As such, the ATC of the feedback structure requires a low pass filter (LPF) with a very low cutoff frequency to minimize offset errors. That is, R3 and CFB (cipher feedback) must have a very large value. However, in the feedforward ATC according to the embodiment of the present invention, even if the cut-off frequency of the low-pass filter is high, a separate offset canceller that can be controlled automatically or manually from the outside can be configured to minimize the offset error , And a two-stage LPF can be configured to match the values of the passive elements to values that can be implemented within the integrated circuit.

According to the present invention, the optical receiver according to the embodiment of the present invention includes a noise canceling block (NCB) and a feedforward automatic boundary point control block (Auto Threshold) in a single mode optical receiving circuit equipped with an on- Control, ATC) to minimize common-mode noise and offset errors, thereby improving noise characteristics.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

Claims (8)

An automatic boundary point controller for outputting a reference voltage,
An on-chip regulator that generates an on-chip voltage that is lower than the external voltage from an external voltage,
Chip mode, receives the current signal from the photodetector, receives the on-chip voltage from the on-chip regulator, converts the current signal into a voltage signal, and amplifies the voltage signal to output the voltage signal with minimum power- part,
A noise cancellation block for receiving a reference voltage output from the automatic boundary point controller and a common mode voltage output from the preamplifier, adding the sum to the on-chip voltage, and outputting the sum to the preamplifier;
And a peripheral device unit including the on-chip regulator, the automatic boundary point controller, the preamplifier unit, and the band cap reference and theity circuit for providing a bias current and a reference voltage to the noise canceling unit,
And a light receiving device. The method according to claim 1,
And a post-amplification unit operating in a differential mode and disposed at a rear stage of the pre-amplification unit,
Wherein the automatic boundary point controller comprises:
And a feedforward structure for normalizing the reference voltage and outputting the reference voltage as a reference voltage of the postamplifier. 3. The method of claim 2,
The post-amplification unit, and
A first differential amplifier connected to the preamplifier and the postamplifier,
Further comprising: The method of claim 3,
And a low-pass filter for eliminating an offset error of the post-amplifier unit. 5. The method of claim 4,
The post-
A light-receiving device including a three-stage high-speed amplifier or a four-stage high-speed amplifier. 5. The method of claim 4,
A driving unit for driving a transmission line or an input capacitance of the output stage
Further comprising: The method according to claim 6,
An equalizer including a high-pass filter that is inverse to the transfer function of the low-
Further comprising: delete

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