KR100751920B1 - Optical receiver with compact dimension - Google Patents

Abstract

An optical receiver having compact dimension is provided to generate a voltage signal corresponding to an optical signal and a reference voltage in proportion to the amplitude of an input signal in a TIA(Trans-Impedance Amplifier) by using plural amplifiers. An optical receiver having compact dimension comprises the followings: a light detecting unit(100) for generating a current signal corresponding to a received optical signal; a reference current/voltage converting unit(110) for converting the current signal into a voltage signal by using a predetermined resistor and plural amplifiers and generating a reference voltage corresponding to amplitude of the current signal by using the voltage gain ratio between the plural amplifiers; and a logic determination unit(130) for determining a logic level by comparing the reference voltage with amplitude of the voltage signal.

Description

Optical receiver with compact dimension

1 is a block diagram of a light receiving apparatus according to the present invention.

FIG. 2 is a detailed circuit diagram of the reference current voltage converter of FIG. 1.

3 is a block diagram of an optical receiving audio device having the optical receiving device of FIG.

4 is a block diagram of an optical communication device including the optical receiver of FIG. 1.

5 illustrates output signal characteristics of the reference current voltage converter of FIG. 1.

6 is a simulation graph for a logic level output according to the present invention.

7 is a graph showing a pulse width distortion change according to the change of the optical signal of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical communications, and more particularly, to an optical receiving apparatus having a small area, an optical receiving audio apparatus and an optical communication apparatus using the same.

Until recently, the home network sector, which was limited to the use of printers and the Internet, is steadily evolving into a multimedia home network that enables real-time communication between TV, audio, and video due to the rapid growth of ubiquitous networks.

The construction of such a home network is largely carried out by wire and wireless. Among these, an optical link is smaller and lighter than an electric wire, and has a small transmission loss so that a large amount of information can be transmitted regardless of transmission bandwidth. Because of its availability, it is being used to build networks of homes (IEEE 1394), automobiles (media oriented system transports) and offices.

Meanwhile, in order to apply an optical link to a portable device such as a mobile phone or an MP3 player and a medical device, the thin, small and low power of each component becomes a key technology. But up to now. Since the receivers are mostly implemented using the BJT process, they occupy a larger area and consume more power than the CMOS process. Also conventional optical song. The receiver does not meet the data rates required by DVD-Audio (96 오디오, 24bit, Multi-Channel) and SACD (2822.4㎑, 1bit, Multi-Channel).

Recently, the demand for signal processing devices is increasing rapidly due to the digitization of multimedia devices such as DVD players, AC3 amps, STBs, and sound cards. Therefore, by applying a CMOS process to the optical transmission devices required for this, it is necessary to reduce power consumption and to continuously reduce cost.

Conventional photoreceivers are implemented using auto-gain control or auto-threshold control to ensure the wide dynamic range and sensitivity required by the system. However, both techniques use large capacitors to generate accurate reference voltages, increasing chip area and power consumption.

Therefore, conventional optical receivers require a large chip area for implementation, high manufacturing costs, high power consumption during operation, and are unsuitable for the field of portable audio or digital audio, which requires efficiency of area. There is this.

Accordingly, an aspect of the present invention is to provide an optical receiving apparatus having a small area capable of reducing the effective area and manufacturing cost and reducing power consumption during driving.

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In order to achieve the above technical problem, the present invention uses a photodetector for generating a current signal corresponding to the received optical signal, a plurality of amplifiers for inputting the current signal and a predetermined resistor to correspond to the current signal. A reference current voltage converting unit converting the voltage signal into a voltage signal and generating a reference voltage corresponding to the magnitude of the current signal using a voltage gain ratio between the plurality of amplifiers, and comparing the magnitude of the voltage signal with the reference voltage Provided is a light receiving apparatus having a small area including a logic determining unit for determining a level.

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The optical receiver according to the present invention generates a reference voltage together in a TIA circuit, thereby reducing chip area and power consumption.

Hereinafter, with reference to the drawings will be described a preferred embodiment of the present invention.

1 is a block diagram of a light receiving apparatus according to the present invention.

The photodetector 100 generates a current signal corresponding to the received optical signal.

The photodetector 100 may include a photo diode that generates a current signal according to the flow of the carrier absorbing the photon energy of the optical signal.

Photo diodes are a type of optical sensor that converts light energy into electrical energy. The configuration adds a photodetection function to the P-N junction (junction) of the semiconductor. In general, there is a physical interaction between light and a material, and a phenomenon in which a material absorbs photons (light energy) and thus emits electrons is called a photoelectric effect. As a result of the photoelectric effect, a voltage appears at a junction of a semiconductor. It's called an effect. Photons excite electrons in the crystal, resulting in photovoltaics.

If the incident light energy is larger than the bandgap energy Eg, the electrons are attracted to the conductive band and leave holes (holes) in the original valence band. This phenomenon occurs anywhere in the P layer, the depletion layer, and the N layer in the device. In the depletion layer, electrons move to the N layer due to the action of the electric field, and electrons of the generated electric energy move together in the P layer. Gather at the Floor Challenge. In other words, in the photodiode, a positive type is charged in the P layer and negative in the N layer in proportion to the incident light, thereby forming a kind of generator.

Photodiodes include PN diodes, PIN diodes, and metal semiconductor metal diodes.

The reference current voltage converting unit 110 includes a plurality of amplifiers and predetermined resistors as inputs of the current signal generated by the photodetector 100.

The reference current voltage converter 110 converts the current signal into a corresponding voltage signal using a plurality of amplifiers and a predetermined resistor. In addition, the reference current voltage converter 110 generates a reference voltage corresponding to the magnitude of the current signal by using the voltage gain ratio between the plurality of amplifiers.

The logic determiner 130 determines the logic level Vout by comparing the magnitude of the voltage signal generated by the reference current voltage converter 110 with a reference voltage.

Preferably, the light receiving device according to the present invention may include a level shifting part 120. The level shifter 120 amplifies the magnitude of the voltage signal and the reference voltage generated by the reference current voltage converter 110 to a size corresponding to the input voltage range of the logic determiner 130.

FIG. 2 is a detailed circuit diagram of the reference current voltage converter 110 of FIG. 1.

FIG. 2 illustrates an example of using a five stage amplifier to obtain a high voltage gain in the reference current voltage converter 110.

At this time, if the number of amplifiers used is too large, the possibility of oscillation may increase. Conversely, if the number of amplifiers used is too small, a low voltage gain is obtained.

The resistor 216 converts the current signal Iin according to the optical signal into a voltage signal Vo.

At this time, the voltage gain A of the reference current voltage converter is as follows.

At this time, A1, A2, A3, A4 and A5 are voltage gains between the input terminal and the output terminal of each amplifier.

The plurality of amplifiers 211-215 are connected between an inverter circuit including two transistors M1 and M3 having gate terminals connected to each other, and an output node and ground of the inverter circuit to add a predetermined impedance. The impedance unit M2 may be included.

In this case, as shown in FIG. 2, the impedance unit may include at least one transistor M2 having a gate terminal and a source terminal connected to an output node of the inverter circuit and a drain terminal connected to the ground.

At this time, the voltage gain A1 of the first amplifier 211 is as follows.

는 i

번째 트랜지스터의 트랜스 컨덕턴스(transconductance)를 나타낸다. 키르히호프(Kirchoff)의 법칙, PMOS 트랜지스터의 트랜스 컨덕턴스와 드레인 전류 i, 게이트 전압 Vgs, 문턱 전압 Vt 사이의 관계식

을 이용하면 A1은 다음과 간단하게 나타낼 수 있다.At this time,

I

The transconductance of the first transistor is shown. Kirchoff's law, the relationship between the transconductance and drain current i, gate voltage Vgs, and threshold voltage Vt of a PMOS transistor

Using A1 can be expressed simply as

를 나타내고, W은 채널의 폭, L은 채널의 길이를 나타낸다. 여기서, PMOS 트랜지스터와 NMOS 트랜지스터의 캐리어 모빌리티(mobility)에 관한 공정 파라미터(parameter)인

항은 제곱근 형태를 가지므로, 공정 파라미터(parameter)에 의한 영향을 줄이기 위해 C보다 B를 크게 설계할 수 있다.At this time,

Where W is the width of the channel and L is the length of the channel. Here, a process parameter relating to carrier mobility of the PMOS transistor and the NMOS transistor is

Since the term has a square root form, B can be designed larger than C to reduce the effect of process parameters.

In addition, A2, A3, A4, A5 can also be expressed in the same way as A1.

The reference current voltage converter of FIG. 2 generates a reference voltage Vref that is 1/2 of the final output voltage by using a difference between the voltage gain up to the third stage and the voltage gain up to the fifth stage. The relationship between the voltage gains from the third stage to the fifth stage can be expressed as follows.

In this case, A1 to 5 represent the voltage gain from the first stage to the fifth stage, A1 to 3 represent the voltage gain from the first stage to the third stage, and A4 to 5 represent the fourth stage to the fifth stage. Denotes the voltage gain.

Preferably, when five amplifiers are used in the reference current voltage converting unit as shown in FIG. 2, when the product of the voltage gains of the fourth and fifth stages is two, the output voltage, that is, one of the voltage signals Vo The reference voltage Vref corresponding to / 2 may be generated.

The plurality of amplifiers 211-215 are connected in series as shown in FIG. 2, the voltage signal Vo is output at the final output node of the plurality of amplifiers 211-215, and the reference voltage Vref is provided in plurality. It may be output at any one of the nodes connecting the amplifiers (211-215).

3 is a block diagram of an optical receiving audio device having the optical receiving device of FIG.

The photo detector 300 generates a current signal corresponding to the received optical signal.

The reference current voltage converting unit 310 includes a plurality of amplifiers and predetermined resistors as inputs of the current signal generated by the photodetector 300. The reference current voltage converter 310 converts the current signal into a corresponding voltage signal using a plurality of amplifiers and predetermined resistors, and uses a reference corresponding to the magnitude of the current signal using a voltage gain ratio between the plurality of amplifiers. Generate a voltage.

Preferably, the reference current voltage converter 310 may be designed such that the voltage gain of the node where the voltage signal is output is doubled compared with the voltage gain of the node where the reference voltage is output.

The logic determiner 330 determines the logic level by comparing the magnitude of the voltage signal with the reference voltage.

The signal processor 340 outputs an audio signal by performing a predetermined audio signal process on data according to a logic level determined by the logic determiner 330.

The speaker unit 350 outputs an audio signal in the form of sound waves and transmits the audio signal to a listener's ear.

Preferably, the optical receiving audio device according to the present invention may include a level shifter 120. The level shifter 120 amplifies the magnitude of the voltage signal and the reference voltage generated by the reference current voltage converter 310 to a magnitude corresponding to the input voltage range of the logic determiner 330.

4 is a block diagram of an optical communication device including the optical receiver of FIG. 1.

The photo detector 400 receives the optical signal received from the optical fiber 401 and generates a current signal corresponding to the received optical signal.

The reference current voltage converting unit 410 includes a plurality of amplifiers and a predetermined resistor for inputting a current signal generated by the photodetector 400. The reference current voltage converter 410 converts the current signal into a corresponding voltage signal using a plurality of amplifiers and predetermined resistors, and corresponds to a magnitude of the current signal using a voltage gain ratio between the plurality of amplifiers. Generate a reference voltage.

Preferably, the reference current voltage converter 410 may be designed such that the voltage gain of the node where the voltage signal is output is doubled compared with the voltage gain of the node where the reference voltage is output.

The logic determiner 430 determines the logic level by comparing the magnitude of the voltage signal with the reference voltage.

The buffer 460 sequentially stores data about a logic level determined by the logic determination unit 430.

The data recovery unit 470 restores the data transmitted to the transmission terminal of the optical signal by using the data for the logic level stored in the buffer 460.

Preferably, the optical communication device according to the present invention may include a level shifter 120. The level shifter 120 amplifies the magnitude of the voltage signal and the reference voltage generated by the reference current voltage converter 410 to a magnitude corresponding to the input voltage range of the logic determiner 430.

FIG. 5 illustrates output signal characteristics of the reference current voltage converter 110 of FIG. 1.

When the intensity of the optical signal is low (Low-power input), the magnitude of the corresponding voltage signal Vo is small. As a result, the reference voltage Vref is also reduced.

On the contrary, when the intensity of the optical signal is high (high-power input), the magnitude of the corresponding voltage signal Vo is large. As a result, the reference voltage Vref also increases.

이하가 된다. 따라서, 종래의 광수신 장치에 비해 2배 정도 감소된 면적을 차지하며, 9mW 이하의 낮은 전력을 소모한다. 이렇게 시제품으로 구현된 광수신 장치는 DC~40Mbps까지의 동작 주파수를 가진다. 이와 같은 시제품의 스펙을 표로 정리하면 다음과 같다.If the optical receiver according to the present invention is implemented as a chip using a 0.25um standard CMOS process, the effective area of the prototype is

It becomes as follows. Therefore, it occupies an area reduced by about 2 times compared with the conventional optical receiver, and consumes low power of 9 mW or less. The optical receiver implemented as a prototype has an operating frequency from DC to 40Mbps. The specifications of such a prototype are summarized as follows.

Chip size 270 × 120um ² Input current 400nA ~ 2000nA Operating frequency DC to 40 Mbps Power consumption Up to 9 mW Supply voltage 2.5V fair 0.25um CMOS

However, the content of Table 1 is only one example of implementing the present invention, it is possible to further reduce the effective area and power consumption according to the manufacturing process. As such, the effective area and power consumption may be reduced by not using a large capacitor to generate a reference voltage, and without using a separate reference voltage generator, in the reference current voltage converting units 110, 310, and 410. Vref) and voltage signal Vo are generated simultaneously.

6 is a simulation graph for a logic level output according to the present invention.

6 is a simulation result showing the transient response characteristics according to the amount of light input to the light detection unit (100, 300, 400) of the light receiving device.
The enlarged portion 600 represents a change in the reference voltage Vref and the voltage signal Vo according to the change in the amount of light input to the photodetectors 100, 300, and 400. In the enlarged part 600, it can be seen that the reference voltage indicated by the dotted line is 1/2 of the final output voltage, that is, the voltage signal Vo.

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7 is a graph showing a pulse width distortion change according to the change of the optical signal of the present invention.

FIG. 7 illustrates pulse width distortion measured by applying an input current from 400nA to 2000nA to the reference current voltage converters 110, 310, and 410 of the prototype manufactured according to the specifications of Table 1. FIG. According to the present invention, the pulse width distortion is measured within 0.2%, indicating that there is no degradation in performance.

Preferably, the plurality of amplifiers may be composed of a plurality of field effect transistors (FETs).

Preferably, the plurality of amplifiers may be composed of a plurality of dipole junction transistors BJT. In this case, the gate terminal described above may be matched with a base terminal, a source terminal may be an emitter terminal, and a drain terminal may be matched with a collector terminal.

Preferably, the plurality of amplifiers may include an inverter circuit including two transistors whose gate terminals are connected to each other, and an impedance unit connected between an output node and ground of the inverter circuit to add a predetermined impedance.

Preferably, the impedance unit may include at least one transistor having a gate terminal and a source terminal connected to an output node of the inverter circuit, and a drain terminal connected to the ground.

Preferably, the reference current voltage converter is a plurality of amplifiers are connected in series, the voltage signal is output at the final output node of the plurality of amplifiers, the reference voltage is at any one of the nodes connecting the plurality of amplifiers It can be designed to be output.

Preferably, the reference current voltage converter may include a predetermined resistor connected between a final node and a node to which a current signal corresponding to the optical signal is input to convert the current signal into a voltage signal.

Preferably, the reference current voltage converter may be designed such that the voltage gain of the final output node is twice the voltage gain of the node from which the reference voltage is output.

Preferably, the photodetector may include a photodiode for generating the current signal according to the flow of the carrier absorbing the photon energy of the optical signal.

Preferably, the photodiode may comprise a PN diode.

Preferably, the photodiode may comprise a PIN diode.

Preferably, the photodiode may comprise a metal semiconductor metal diode.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary and will be understood by those of ordinary skill in the art that various modifications and variations can be made therefrom. However, such modifications should be considered to be within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, according to the present invention, a plurality of amplifiers are used without a large capacitor and a separate reference voltage generator, so that the current voltage converter (TIA) is used to control the reference voltage and the optical signal proportional to the magnitude of the input signal. By generating the corresponding voltage signal, it is possible to reduce the effective area and manufacturing cost of the light receiving device and to reduce the power consumption during driving, without increasing the pulse width distortion.

Claims (13)

A photo detector for generating a current signal corresponding to the received optical signal; The current signal is converted into a corresponding voltage signal by using a plurality of amplifiers and a predetermined resistor as the current signal, and the voltage gain ratio between the plurality of amplifiers corresponds to the magnitude of the current signal. A reference current voltage converting unit generating a reference voltage; And And a logic determiner configured to determine a logic level by comparing the magnitude of the voltage signal with the reference voltage. The method of claim 1, And a level shifting unit configured to amplify the magnitudes of the voltage signal and the reference voltage to a magnitude corresponding to an input voltage range of the logic determination unit. The method of claim 1, The plurality of amplifiers An inverter circuit including two transistors whose gate terminals are connected to each other; And And an impedance unit connected between the output node of the inverter circuit and the ground to add a predetermined impedance. The method of claim 3, wherein The impedance unit And at least one transistor having a gate terminal and a source terminal connected to an output node of the inverter circuit, and a drain terminal connected to the ground. The method of claim 1, The reference current voltage conversion unit The plurality of amplifiers are connected in series, the voltage signal is output at the final output node of the plurality of amplifiers, and the reference voltage is output at any one of the nodes connecting between the plurality of amplifiers Photoreceiving device. The method of claim 5, The reference current voltage conversion unit And a predetermined resistor connected between the final node and a node to which a current signal corresponding to the optical signal is input to convert the current signal into the voltage signal. The method of claim 5, The reference current voltage conversion unit And a voltage gain of the final output node is twice the voltage gain of the node at which the reference voltage is output. The method of claim 1, The light detector is And a photodiode for generating the current signal according to the flow of the carrier absorbing the photon energy of the optical signal. The method of claim 8, The photodiode is An optical receiving device, characterized in that a PN diode. The method of claim 8, The photodiode is Optical receiving device, characterized in that the PIN diode. The method of claim 8, The photodiode is It is a metal semiconductor metal diode, The optical receiving device characterized by the above-mentioned. delete delete

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