KR101513372B1 - Optical receiver for adjusting gain or transconductance - Google Patents

Abstract

Disclosed is an optical communications receiver including a circuit, which adjusts gain or transconductance of a preamplifier. The optical communications receiver includes: an optical signal reception device; an amplifier into which photocurrent, output from the optical signal reception device, is input; and a gain adjustment unit which is connected to the amplifier and adjusts gain of the amplifier. A resistance value of the gain adjustment unit varies depending on whether the unit is in an overcurrent condition or a normal condition.

Description

[0001] OPTICAL RECEIVER FOR ADJUSTING GAIN OR TRANSCONDUCTANCE [0002]

The present invention relates to an optical communication receiver.

The optical communication receiver receives the optical signal from the optical communication transmitter, converts it into a photocurrent, and outputs it.

Conventional optical communication receivers bypass the AC signal using a capacitor when an overload current is input from the photodiode to design a high dynamic range. However, this method can degrade the bandwidth performance of the optical communication receiver by generating parasitic capacitors.

Korean Patent Publication No. 2006-0013899 (Published on February 14, 2006)

SUMMARY OF THE INVENTION The present invention provides an optical communication receiver including a circuit for regulating the gain or transconductance of the preamplifier.

According to an aspect of the present invention, there is provided an optical communication receiver including: an optical signal receiving element; An amplifier for receiving the optical current output from the optical signal receiving element; And a gain adjusting unit connected to the amplifier, the gain adjusting unit adjusting a gain of the amplifier. Here, the value of the resistance of the gain control unit is different between the overcurrent state and the normal state.

According to another aspect of the present invention, there is provided an optical communication receiver including: an optical signal receiving element; An amplifier for receiving the optical current output from the optical signal receiving element; And a transconductance adjuster connected to the amplifier to adjust the transconductance of the amplifier.

A receiver according to an embodiment of the present invention includes an amplifier; A feedback resistor connected between the input and output of the amplifier; And a switch connected in parallel with the feedback resistor. Here, when the overcurrent is input to the amplifier, the switch is turned on and the feedback resistor is inactivated.

According to another aspect of the present invention, there is provided a receiver including: an amplifier; A switch coupled to the amplifier; And an overcurrent compensation circuit. Here, when an overcurrent is input to the amplifier, a current flowing in the amplifier is discharged through the switch according to a signal output from the overcurrent compensation circuit.

The optical communication receiver according to the present invention can adjust the gain of the preamplifier by varying the value of the feedback resistance of the preamplifier when the overcurrent is input.

In addition, the optical communication receiver may regulate the transconductance of the preamplifier by discharging at least a part of the current in the preamplifier when an overcurrent is input.

1 is a diagram illustrating an optical communication receiver according to a first embodiment of the present invention.
Fig. 2 is a circuit diagram of the optical communication receiver of Fig. 1 according to the first embodiment of the present invention.
Fig. 3 is a circuit diagram of the optical communication receiver of Fig. 1 according to the second embodiment of the present invention.
4 is a diagram illustrating an optical communication receiver according to a second embodiment of the present invention.
5 is a circuit diagram of the optical communication receiver of FIG. 4 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.

The present invention relates to an optical communication receiver capable of adjusting a gain of a transimpedance amplifier (TIA) and adjusting a transconductance (g _m ) in an overcurrent input. Here, the overcurrent is a concept including an overload current.

For example, when an overcurrent is input to a preamplifier (TIA), the present invention may adjust the gain of the preamplifier (TIA) by varying the feedback resistance of the preamplifier (TIA).

In addition, the present invention can control the transconductance (g _m) of the preamplifier (TIA) when the input over-current, and as a result it is possible to realize a wide-band and an optical communication receiver having a wide dynamic range (dynamic range).

Of course, basically, when the optical current output from the optical signal receiving device, for example, a photodiode (PD) is an overcurrent equal to or higher than a predefined value, the optical communication receiver does not reach the saturation state of the preamplifier A portion of the photocurrent input to the preamplifier (TIA) may be discharged to the ground.

Hereinafter, various embodiments of the optical communication receiver of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating an optical communication receiver according to a first embodiment of the present invention.

Referring to FIG. 1, the optical communication receiver of the present embodiment includes a photodiode PD, an amplifier 100, for example, a preamplifier, an overcurrent compensation circuit 102, and a gain controller 104.

The photodiode PD receives the optical signal transmitted from the optical communication transmitter, converts the received optical signal into an electric signal (photocurrent), and outputs the electric signal.

The amplifier 100 amplifies and outputs the weak photocurrent supplied from the photodiode PD with a sufficient gain.

The overcurrent compensation circuit 102 can compensate the overcurrent so that the amplifier 100 does not reach the saturation state due to the overcurrent when the photocurrent output from the photodiode PD is an overcurrent equal to or higher than a predetermined value. For example, the overcurrent compensation circuit 102 may discharge at least a portion of the photocurrent output from the photodiode PD through the ground to reduce the amount of current input to the amplifier 100 in the case of an overcurrent, The amount of current input to the resultant amplifier 100 becomes small.

The gain control unit 104 is connected between the input and output of the amplifier 100, that is, it is a feedback circuit. For example, the gain adjuster 104 may vary the value of the resistance according to a signal provided from the overcurrent compensating circuit 102 when the overcurrent is inputted, thereby reducing the gain of the amplifier 100. [ Of course, the gain control unit 104 may vary the value of the resistance according to a signal transmitted from a circuit other than the signal transmitted from the overcurrent compensation circuit 102. [

According to one embodiment, the value of the resistance of the gain control unit 104 when in the overcurrent state may be smaller than the value of the resistance of the gain control unit 104 in the steady state. A detailed description thereof will be described later.

In summary, the optical communication receiver of the present embodiment can vary the gain of the preamplifier 100 by varying the value of the resistance of the gain controller 104 in the overcurrent state.

Fig. 2 is a circuit diagram of the optical communication receiver of Fig. 1 according to the first embodiment of the present invention.

2, the optical communication receiver of the present embodiment includes a photodiode (PD), a preamplifier 100, an overcurrent compensation circuit 102, and a gain compensation unit 104.

The overcurrent compensation circuit 102 compensates the overcurrent when the current output from the photodiode PD is an overcurrent equal to or greater than a predetermined value.

According to one embodiment, the overcurrent compensation circuit 102 includes a first transistor M1 and a second transistor M2 as first mirror circuits, a third transistor M3 and a fourth transistor M4 as second mirror circuits, . ≪ / RTI > Of course, although not shown, the first transistor M1 and the fourth transistor M4 may be connected between the first transistor M1 and the voltage source V _DD , between the second transistor M2 and the voltage source V _DD , between the third transistor M3 and ground, A first resistor, a second resistor, a third resistor, and a fourth resistor may be formed between the first resistor and the ground.

The voltage source V _DD serves to supply a predetermined voltage, for example, 5 V, to the overcurrent compensation circuit 102.

The first mirror circuit may include transistors M1 and M2 of a mirror structure and each of the MOS transistors M1 and M2 may be a p-MOS transistor.

The first transistor M1 is connected between the voltage source Vs and the photodiode PD and operates in response to a voltage supplied from the voltage source V _DD . In this case, the current i flows through the first transistor M1. For example, the gate of the first transistor M1 may be coupled to the drain, and the source may be coupled to the first resistor.

The second transistor M2 forms a mirror structure with the first transistor M1, the gate thereof is connected to the gate of the first transistor M1, and the source thereof is connected to the second resistor M1.

Since the first mirror circuit is a mirror structure, a current proportional to the current (i) or the current (i) flowing through the first transistor (M1) can flow through the second transistor (M2). The magnitude of the current flowing through the second transistor M2 may be determined by the size of the transistors M1 and M2.

The second mirror circuit includes transistors M3 and M4 having a mirror structure and emits a current when the photocurrent output from the photodiode PD is an overcurrent. Accordingly, the second mirror circuit can be named as an overcurrent compensator have. Each of the MOS transistors M3 and M4 may be an N-MOS transistor.

The source of the third transistor M3 may be coupled to ground through a third resistor and the drain may be coupled to the photodiode PD and the preamplifier 100. As a result, a part of the current output from the photodiode PD can flow through the third transistor M3.

The gate of the fourth transistor M4 may be connected to the gate of the third transistor M3, the gate may be connected to the drain, and the source may be connected to the ground through the fourth resistor. As a result, the current flowing through the second transistor M2 can flow to the ground through the fourth transistor M4.

Here, the magnitude of the current flowing through the inside of the transistors M3 and M4 may vary depending on the size ratio of the third transistor M3 and the fourth transistor M4. That is, if the size of the third transistor M3 is larger than the size of the fourth transistor M4, the amount of current flowing in the third transistor M3 is larger than the amount of current flowing in the fourth transistor M4, If the size of the third transistor M3 is smaller than the size of the fourth transistor M4, the amount of the current flowing through the third transistor M3 is smaller than the amount of the current flowing through the fourth transistor M4. The size of the NMOS transistor is determined by the width and length of the gate of the NMOS transistor. Specifically, it is proportional to the width of the gate and inversely proportional to the length of the gate. Meanwhile, the widths and lengths of the gates of the transistors M3 and M4 included in the second mirror circuit may have the same value.

The third resistor is connected between the source of the third transistor M3 and the ground to adjust the current flowing through the third transistor M3. Here, if the resistance value of the third resistor is large, the current decreases, and if the resistance value of the third resistor is small, the current flowing in the third transistor M3 increases.

The fourth resistor is connected between the source of the fourth transistor M4 and the ground to control the current flowing through the fourth transistor M4.

Hereinafter, the operation of the overcurrent compensation circuit 102 will be described.

When a voltage is supplied from the voltage source (V _DD ), the first mirror circuit and the second mirror circuit start to operate.

Since the first mirror circuit has a mirror structure, the current i output from the photodiode PD flows through the second transistor M2.

Since the current controlled by the fourth resistor flows through the fourth transistor M4 and the second mirror circuit has the mirror structure, the current flowing through the fourth transistor M4 through the third transistor M3 The current flows in the same or proportional manner.

In this overcurrent compensation circuit 102, when the current output from the photodiode PD is an overcurrent, the magnitude of the current flowing through the fourth transistor M4 increases. As a result, the voltage of the node corresponding to the gate of the fourth transistor M4 rises, and as a result, the voltage of the gate of the fourth transistor M4 rises. Therefore, the current flowing to the third transistor M3 is increased, and as a result, the magnitude of the current input to the preamplifier 100 is reduced. Therefore, even in the case of the overcurrent, the preamplifier 100 can operate stably.

Referring again to FIG. 2, the gain adjustment unit 104 may include a feedback resistor R and a switch, for example, a fifth transistor M5.

The feedback resistor R is connected between the input and output of the preamplifier 100.

The fifth transistor M5 is connected in parallel to the feedback resistor R, for example, an N-MOS transistor.

The operation of the gain control unit 104 is as follows. In the normal state, since the voltage of the node where the gates of the transistors M3 and M4 meet is low, that is, low logic, It is not turned on. As a result, the feedback resistor R connected between the input and output of the preamplifier 100 is activated.

On the other hand, in the overcurrent state, the voltage at the node where the gates of the transistors M3 and M4 meet increases, that is, changes to High logic, so that the fifth transistor M5 is turned on. As a result, the input and output stages of the preamplifier 100 are short-circuited, and the feedback resistor R is inactivated. That is, the feedback resistor R varies depending on the current state.

Since the gain of the preamplifier 100 is proportional to the feedback resistance R, the gain of the preamplifier 100 is reduced in the overcurrent state.

In summary, in the optical communication receiver of the present embodiment, the gain adjuster 104 short-circuits the input and output terminals of the preamplifier 100 according to the signals output from the overcurrent compensation circuit 102 during the overcurrent, The gain can be reduced. Thus, the performance of a wide dynamic range optical communication receiver can be realized.

Fig. 3 is a circuit diagram of the optical communication receiver of Fig. 1 according to the second embodiment of the present invention.

Referring to FIG. 3, the optical communication receiver of the present embodiment includes a photodiode PD, a preamplifier (TIA), an overcurrent compensation circuit, and a gain controller 104.

The remaining components except for the gain adjusting unit 104 are the same as those in the first embodiment, and the description will be omitted.

The gain control unit 104 may include a first feedback resistor R1, a second feedback resistor R2, and a fifth transistor M5.

Feedback resistors R1 and R2 are connected in series between the input and output of the preamplifier (TIA).

The fifth transistor M5 is connected in parallel to the first feedback resistor R1.

In the steady state, since the fifth transistor M5 is in the off state, both the feedback resistors R1 and R2 are activated.

On the other hand, in the overcurrent state, the fifth transistor M5 is turned on, so that the first feedback resistor R1 is inactivated and only the second feedback resistor R2 is activated. As a result, the value of the feedback resistance in the overcurrent state becomes smaller than the value of the feedback resistance in the steady state.

2 and 3, the value of the feedback resistance of the preamplifier (TIA) changes in the steady state and the overcurrent state, and as a result, the gain of the preamplifier (TIA) is adjusted.

4 is a diagram illustrating an optical communication receiver according to a second embodiment of the present invention.

4, the optical communication receiver of the present embodiment includes a photodiode PD, a preamplifier 400, an overcurrent compensation circuit 402, a gain controller 404, and a transconductance controller 406.

The remaining components except for the transconductance adjuster 406 are the same as those in the first embodiment, and the description will be omitted.

Transconductance control unit 406 controls the transconductance (g _m) of the pre-amplifier 400 to adjust the current within the preamplifier 400

According to one embodiment, the transconductance adjuster 406 may discharge at least a part of the current flowing into the preamplifier 400 to the ground according to a signal provided from the overcurrent compensating circuit 402 at the time of an overcurrent. As a result, the transconductance (g _m ) of the preamplifier 400 is adjusted.

In summary, the optical communication receiver of this embodiment implements a circuit that regulates the gain and transconductance (g _m ) of the preamplifier 400.

5 is a circuit diagram of the optical communication receiver of FIG. 4 according to an embodiment of the present invention.

5, the transconductance adjuster 406 may include two switches, for example, transistors M6 and M7, connected in series to a voltage source V _DD .

The sixth transistor M6 may be a P-MOS transistor, and the seventh transistor M7 may be an NMOS transistor. That is, the transistors M6 and M7 switch.

The node where the gates of the transistors M6 and M7 meet is connected to the node where the gates of the transistors M3 and M4 meet.

In addition, a node where the drains of the transistors M6 and M7 meet can be connected to the first stage of the preamplifier 400, for example, to the emitter of the transistor T. [

Hereinafter, the operation of the transconductance adjuster 406 will be described.

In the steady state, the voltage at the node where the gates of the transistors M3 and M4 meet is low, i.e., low logic, so that the sixth transistor M6 is turned on and the seventh transistor M7 is off. However, a voltage source (V _DD), but the current to flow through the sixth transistor (M6) by the supply voltage from, the present invention is a size of the sixth transistor (M6) is the electric current does not flow in the pre-amplifier 400, It can be designed properly.

The sixth transistor M6 is turned off and the seventh transistor M7 is turned on because the voltage at the node where the gates of the transistors M3 and M4 rises, Is turned on. As a result, the current of the preamplifier 400 is discharged to the ground through the seventh transistor M7. As a result, the transconductance (g _m ) of the preamplifier 400 is adjusted.

In short, the optical communication receiver example of this embodiment controls the transconductance (g _m) of the excess current when the pre-amplifier to release a current of 400, a preamplifier 400.

It will be apparent to those skilled in the art that various modifications, additions and substitutions are possible, without departing from the spirit and scope of the invention as defined by the appended claims. Should be regarded as belonging to the following claims.

PD: photodiode 100, 400: preamplifier
102, 402: overcurrent compensation circuit 104, 404: gain control section
406: transconductance adjuster

Claims (15)

An optical signal receiving element;
An amplifier for receiving the optical current output from the optical signal receiving element;
A gain controller connected to the amplifier, the gain controller adjusting a gain of the amplifier; And
And an overcurrent compensation circuit that discharges at least a part of a photocurrent input to the amplifier through an earth when the overcurrent state is present,
Wherein a value of a resistance of the gain control unit is different between the overcurrent state and the steady state, and when a voltage of a node of the overcurrent compensation circuit connected to the gain control unit increases in the overcurrent state, And is smaller than a resistance value of the gain adjusting section when the gain control section is in the steady state. delete delete The apparatus of claim 1,
A feedback resistor connected between the input and output of the amplifier; And
And a transistor coupled in parallel to the feedback resistor,
The gate of the transistor is connected to the node, and when the voltage of the node rises due to the overcurrent state, the transistor is turned on, the feedback resistor is inactivated, and the input and output terminals of the amplifier are short- Lt; / RTI > The apparatus of claim 1,
A first feedback resistor and a second feedback resistor connected between the input and output of the amplifier; And
And a transistor coupled in parallel to the first feedback resistor,
Wherein the gate of the transistor is coupled to the node and when the voltage of the node rises due to the overcurrent condition the transistor is turned on to deactivate the first feedback resistor. The method according to claim 1,
And a transconductance adjuster connected to the amplifier for adjusting a transconductance of the amplifier,
And a current flowing in the amplifier is discharged to the ground through the transconductance controller according to a signal output from the overcurrent compensating circuit when the current is in the overcurrent state. The apparatus of claim 6, wherein the transconductance adjuster comprises:
A first transistor coupled to the voltage source; And
And a second transistor coupled to the first transistor,
Wherein the first transistor and the second transistor are switched and when a voltage of the specific node of the overcurrent compensation circuit rises when the overcurrent state is reached, a node where the gates of the transistors meet is connected to the specific node, Wherein when the voltage of the specific node rises, a current flowing in the amplifier is discharged to the ground through the second transistor. An optical signal receiving element;
An amplifier for receiving the optical current output from the optical signal receiving element; And
And a transconductance adjuster coupled to the amplifier to adjust the transconductance of the amplifier,
And the current flowing into the amplifier when the current is in an overcurrent state is discharged to the ground through the transconductance adjuster. 9. The optical receiver of claim 8, wherein the optical signal receiving element is a photodiode and the amplifier is a preamplifier. The apparatus of claim 8, wherein the transconductance adjuster comprises:
A first transistor coupled to the voltage source; And
And a second transistor coupled to the first transistor,
Wherein the first transistor and the second transistor are operated in a switching operation and the voltage of a specific node of the overcurrent compensation circuit rises when the overcurrent state is established, a node where the gates of the transistors meet are connected to the specific node, When the voltage of the specific node rises, a current flowing in the amplifier is discharged to the ground through the second transistor. delete delete delete amplifier;
A switch coupled to the amplifier; And
An overcurrent compensation circuit,
And a current flowing to the amplifier is discharged to the ground through the switch according to a signal output from the overcurrent compensation circuit when an overcurrent is input to the amplifier. 15. The overcurrent compensation circuit according to claim 14,
A first transistor and a second transistor having a mirror structure; And
And an overcurrent compensation circuit having a third transistor and a fourth transistor having a mirror structure,
The switch is connected to a node where the gate of the third transistor and the gate of the fourth transistor meet, the voltage of the node rises upon the overcurrent input, and when the voltage of the node rises due to the overcurrent input, And the receiver is turned on.

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