JP2000341054A - Optical signal amplifier circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical signal amplifier circuit that can amplify a signal representing a large fluctuation in a change in an input current without deteriorating the S/N even when the amplitude of the signal current is small and without causing saturation even when the amplitude of the signal current is large at a desired gain in the case of reproduction where data are read from an optical information recording medium. SOLUTION: This optical signal amplifier circuit is provided with a 1st amplifier circuit section 3-1 where an input signal current is given to a 1st feedback resistor and which outputs a voltage converted from the current by the 1st feedback resistor, a 2nd amplifier section 3-2 where the input signal current is given to a 2nd feedback resistor and which outputs a voltage converted from the current by the 2nd feedback resistor, a 1st switch SW1 and a 2nd switch SW2 that turn on/off the operation of the 1st and 2nd amplifier sections respectively. The resistance of each feedback resistor is selected depending on a level of the input signal and the 1st and 2nd switches are turned on/off to switch the 1st and 2nd amplifier sections.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal amplifier circuit for converting a photocurrent of a light receiving element for converting reflected light from an optical information recording medium into an electric signal to a desired voltage.

[0002]

2. Description of the Related Art Conventionally, an optical information recording medium is irradiated with light to perform reproduction, recording, or erasing. Is generally used as an optical signal amplifying circuit for converting the signal into a desired voltage. In this optical signal amplifier circuit, as shown in FIG. 3, the base is connected to the input terminal 101, the collector is connected to the power supply VCC via the resistor R101, and the emitter is GN.
Transistor Q101 connected to D and one end is an input terminal
A feedback resistor Rf101 connected to the output terminal 102, the other end of which is connected to the output terminal 102, the base connected to the collector of the transistor Q101, the collector connected to the power supply VCC, and the emitter connected to the output terminal 102. ,
One end is connected to the output terminal 102 and the other end is connected to a resistor R102 connected to GND. The anode of the photodiode PD is connected to the input terminal 101 via the coupling capacitor C. Note that R is a load resistance connected to the anode of the photodiode PD.

[0005] Next, the operation of the optical signal amplifying circuit thus configured will be described. Assuming that the reflected light from the recording medium changes and the photocurrent of the photodiode PD increases by Iin, the input terminal 101 is supplied with the input current Iin. This input current Iin is supplied to a resistor R through a feedback resistor Rf101.
And the input current Iin across the feedback resistor Rf101.
Generates a voltage of a magnitude corresponding to. At this time, the input terminal
One end of the feedback resistor Rf103 corresponding to 101 is fixed to a constant bias given by the base-emitter voltage V _{BE (Q101)} of the transistor Q101. Therefore, the feedback resistor R
Voltage Vout of the output terminal 102 is a connection point between f101 and the resistor R102 is the value of the feedback resistor Rf101 When Rf _101, represented by the following formula (1). _{Vout = V BE (Q101) -Rf} 101 × Iin ··········· (1)

[0004]

However, in the above-mentioned conventional optical signal amplifier circuit, when data is read from the optical information recording medium and reproduced, the signal whose change amount largely changes depending on the read portion is not changed even if the signal current amplitude is small. No consideration is given to the viewpoint of amplifying with a desired gain without deteriorating / N and without saturating the output even when the signal current amplitude is large. For example, at the time of reproduction for reading data from a magneto-optical disk, depending on the disk, the reflected light at the address portion may be several times larger than the reflected light at the data portion. In this case, the current input to the optical signal amplifier circuit also changes several times, and if the value of the feedback resistor Rf101 is set according to the signal from the data section, the output is saturated by the signal from the address section. . Also, if the value of the feedback resistor Rf101 is set small in accordance with the signal from the address section, the influence of noise from the surroundings due to an increase in the noise of the amplifier itself and a decrease in the output amplitude for the signal from the data section increases, and N deteriorates.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem in the conventional optical signal amplifying circuit. It is an object of the present invention to provide an optical signal amplifying circuit capable of amplifying at a desired gain without deteriorating the S / N even when the amplitude is small and saturating the output even when the signal current amplitude is large.

[0006]

According to a first aspect of the present invention, there is provided an optical information recording / reproducing apparatus for reproducing / recording / erasing by irradiating an optical information recording medium with light. A light receiving element for detecting light reflected from the medium, wherein the light signal amplifying circuit converts a photocurrent from the light receiving element to a voltage, wherein a base is connected to the input terminal, and a collector is connected to the first power supply. An input unit including a first transistor connected to the first transistor, one end of which is connected to the emitter of the first transistor, and the other end of which is connected to a second power supply, and a base connected to the first transistor. A second transistor having an emitter connected to the second power supply, a collector connected to the first power supply via a second resistor, and a base connected to the second transistor. A third transistor having a collector connected to the first power supply, a third resistor having one end connected to the emitter of the third transistor, and one end connected to the third transistor. A first amplifying unit comprising a first feedback resistor connected to the emitter of the first transistor and having the other end connected to the base of the first transistor; and a base connected to the emitter of the first transistor; An emitter is connected to the second power supply, a collector is connected to the first power supply via a fourth resistor, and a base is connected to a collector of the fourth transistor. A fifth transistor connected to the first power supply, a fifth resistor having one end connected to the emitter of the fifth transistor, and an end connected to the emitter of the fifth transistor; A second amplifying unit connected to the first feedback resistor, the other end of which is connected to the base of the first transistor, and a second feedback resistor having a different resistance value; A sixth transistor connected to the base of the fifth transistor, and a seventh transistor connected to the base of the fifth transistor.
And a sixth resistor having one end connected to the emitter of the sixth transistor, the other end connected to the other end of the third resistor, and one end connected to the emitter of the seventh transistor. A seventh resistor having the other end connected to the other end of the fifth resistor, one end connected to the collectors of the sixth transistor and the seventh transistor, and the other end connected to the first power supply. And a base connected to one end of the eighth resistor, a collector connected to the first power supply, and an emitter connected to the output terminal.
And an output portion including one end connected to the output terminal and the other end connected to the ninth resistor connected to the second power supply, and one end connected to the other end of the third resistor. A first switch having the other end connected to the second power supply, and a second switch having one end connected to the other end of the fifth resistor and the other end connected to the second power supply. A tenth resistor having one end connected to the base of the sixth transistor, the other end connected to one end of the second switch, and one end connected to the base of the seventh transistor; And a gain switching section composed of an eleventh resistor connected to one end of the first switch.

In the optical signal amplifier configured as described above, for example, when the resistance value of the first feedback resistor is set to be larger than that of the second feedback resistor, and when the amplitude of the input signal current is small during reproduction, the first feedback resistor is set to the first feedback resistance. Is turned on, the second switch is turned off, the input signal current is operated to be supplied to the first feedback resistor, and converted into a voltage by the first feedback resistor and output. On the other hand, when the amplitude of the input signal current is large at the time of reproduction, the first switch is turned off, the second switch is turned on, and the operation is performed so as to supply the input signal current to the second feedback resistor. The voltage is converted by a resistor and output. Therefore, by setting the values of the first feedback resistor and the second feedback resistor according to the levels of the respective input signal currents, even if the signal current amplitude is small, S / S
N can be amplified with a desired gain without deteriorating N and saturating the output even when the signal current amplitude is large.

According to a second aspect of the present invention, in the optical signal amplifier circuit according to the first aspect, the first switch has a collector connected to the other end of the third resistor and an emitter connected to the second power supply. And a ninth transistor having a base to which a first control signal is input, wherein the second switch has a collector connected to the other end of the fifth resistor,
An emitter is connected to the second power supply, and the base is constituted by a tenth transistor having a second control signal input thereto.

In the optical signal amplifying circuit thus configured, when the amplitude of the input signal current is small during reproduction, the first control signal is set to the H level and the second control signal is set to the L level. Turn on the ninth transistor,
The ten transistors are turned off to operate so as to supply an input signal current to the first feedback resistor, and are converted into a voltage by the first feedback resistor and output. On the other hand, when the amplitude of the input signal current is large during reproduction, the ninth control signal is set to the L level and the second
Are turned off and the tenth transistor is turned on to operate to supply the input signal current to the second feedback resistor, and is converted into a voltage by the second feedback resistor and output. Therefore, by setting the values of the first feedback resistor and the second feedback resistor according to the level of each input signal current, the S / N is not degraded even when the signal current amplitude is small, and the signal current is not reduced. Even when the amplitude is large, the signal can be amplified with a desired gain without saturating the output, and an optical signal amplifier circuit including a switch function can be integrated.

[0010]

Next, an embodiment will be described. FIG. 1 is a circuit diagram showing a first embodiment of the optical signal amplifier circuit according to the present invention. This embodiment corresponds to the invention according to claim 1, wherein the base is the input terminal 1.
, A collector connected to a power supply VCC, one end connected to the emitter of the transistor Q1 and the other end connected to a resistor R1 connected to GND, and a base connected to the transistor Q1. The transistor Q2 has an emitter connected to the GND, a collector connected to the power supply VCC via a resistor R2, a base connected to the collector of the transistor Q2, and a collector connected to the power supply VCC. A transistor Q3, a resistor R3 having one end connected to the emitter of the transistor Q3, one end connected to the emitter of the transistor Q3, and the other end connected to the transistor Q3.
The first amplifier 3-1 includes a first feedback resistor Rf1 connected to the first base.

Also, a transistor Q4, a transistor Q5, a resistor R4, and a transistor Q4 having the same configuration as the first amplifying unit 3-1.
A transistor Q6 whose base is connected to the base of the transistor Q3, and a transistor whose base is connected to the base of the transistor Q5, comprising a second amplifying unit 3-2 comprising a resistor R5 and a second feedback resistor Rf2. Q
7, a resistor R6 having one end connected to the emitter of the transistor Q4 and the other end connected to the other end of the resistor R3.
And a resistor R7 having one end connected to the emitter of the transistor Q7 and the other end connected to the other end of the resistor R5.
And one end is connected to the transistor Q6 and the transistor Q7.
And a base connected to one end of the resistor R8, and a base connected to one end of the resistor R8.
A transistor Q8 having a collector connected to the power supply VCC and an emitter connected to the output terminal 2;
And an output unit composed of a resistor R9 whose other end is connected to GND.

Further, a switch SW1 having one end connected to the other end of the resistor R3 and the other end connected to GND, and a switch having one end connected to the other end of the resistor R5 and the other end connected to GND. SW2 and one end of the transistor Q6.
A resistor R10 having the other end connected to one end of the switch SW2 and one end connected to the transistor Q7.
Of the switch SW1 and a resistor R11 connected to one end of the switch SW1 to form an optical signal amplifier circuit. The anode of the photodiode PD functions as the coupling capacitor C. The load resistor R is connected to the input terminal 1 via the input terminal 1 and the anode of the photodiode PD.

Next, the operation of the first embodiment configured as described above will be described. Here, the resistance values Rf ₁ and Rf ₂ of the first and second feedback resistors Rf ₁ and Rf ₂ include:
It is assumed that there is a relationship such as the following equation (2). Rf ₁ > Rf ₂ (2) First, when the amplitude of the input signal current is small during reproduction, the switch SW1 is turned on and the switch SW is turned off.
The resistors R3, R6, and R11 are connected to GND, and one ends of the resistors R5, R7, and R10 are left open. The base potentials of the transistors Q5 and Q7 are determined by the resistors R4 and R11, and the emitter potentials of the transistors Q5 and Q7 are
Since the other end of the resistor R5 is open, no current can flow from the input terminal 1 to the second feedback resistor Rf2, so that the potential becomes higher than the potential of the input terminal 1. Here, the potential Vin of the input terminal 1, the base of the transistor Q2 - emitter voltage V _{BE (Q2),} the base of the transistor Q2 - to-emitter voltage and V _{BE (Q1),} expressed by the following equation (3) . Vin = V _{BE (Q2)} + V _{BE (Q1)} (3)

Therefore, if the resistors R4 and R7 are set so that the base potentials of the transistors Q5 and Q7 are lower than the potential Vin of the input terminal 1, the transistors Q5 and Q7 are turned off. As a result, the first amplifying unit 3-1 operates and the second amplifying unit 3-2 does not operate. The input signal current is the first feedback resistance Rf
1, a voltage having a magnitude corresponding to the input current is generated across the first feedback resistor Rf1, and a potential Vin of the input terminal 1 is generated.
Is fixed in the above equation (3), so that the transistor Q
3 the emitter and will be voltage V ₀₁ of the contacts of the first feedback resistor Rf1 and the resistor R3 varies according to the input current, voltage V ₀₁ at which flowing the input current Iin becomes the following equation (4) . V ₀₁ = Vin−Rf ₁ × Iin (4)

Since the emitter of the transistor Q3 and the emitter of the transistor Q4 have the same potential, the voltage Vout1 output to the output terminal 2 is given by the following equation (5). _{Vout1 = VCC-V 01 × R} 8 / R 6 -V BE (Q8) ······ (5) where the value of R _6, R ₈ are resistors R6 and R8, city these same, Assuming that the base-emitter voltage V _{BE of} each transistor is the same, from equations (3), (4) and (5),
The following equation (6) is obtained. _{Vout1 = VCC + Rf 1 × Iin} -3V BE ········· (6) Therefore, the output terminal 2 voltage determined by the input current Iin and the feedback resistor Rf1 is output.

On the other hand, when the amplitude of the input signal current is large during reproduction, the switch SW1 is turned off and the switch SW1 is turned off.
By turning on 2, the amplifying unit 3-2 operates and the amplifying unit 3-1 does not operate, contrary to the case where the input signal current amplitude is small. Therefore, the output voltage V in this case
out2 is given by the following equation (7). _{Vout2 = VCC + Rf 2 × Iin} -3V BE ········· (7)

As described above, in this embodiment, the switch S
Since the amplifier or the feedback resistor can be selected by W1 and the switch SW2, the first feedback resistor Rf1 and the second feedback resistor Rf1 can be selected according to the level of each input signal current.
By setting the value of the feedback resistor Rf2, it is possible to amplify with a desired gain without deteriorating the S / N even when the signal current amplitude is small, and without saturating the output even when the signal current amplitude is large. it can.

Next, a second embodiment will be described. FIG. 2 is a circuit diagram showing a second embodiment of the optical signal amplifier circuit according to the present invention. This embodiment corresponds to the invention according to claim 2, and the switches SW1 and SW2 in the first embodiment shown in FIG.
The transistor Q9 has a base connected to a control signal VC1 and the transistor Q10 has a base connected to a control signal VC2. Control signals VC1, V
The transistor Q9 and the transistor Q10 can be turned on and off by setting C2 to H level or L level. As a result, the same effects as those of the first embodiment can be obtained, and an optical signal amplifier circuit including a switch function can be integrated.

In each of the above embodiments, an NPN transistor is used as a transistor.
By using a P-type transistor and reversing the power supply to be connected, an optical signal amplifier circuit having the same function and effect can be configured.

[0020]

As described above with reference to the embodiment, according to the first aspect of the present invention, a signal whose change amount largely changes depending on a portion to be read at the time of reading data from an optical information recording medium is reproduced by a signal current. S even if the amplitude is small
/ N can be amplified with a desired gain without deteriorating / N and saturating the output even when the signal current amplitude is large. Further, according to the second aspect of the invention, it is possible to further integrate the optical signal amplifier circuit including the switch function in the first aspect of the invention.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of an optical signal amplifier circuit according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the optical signal amplifier circuit according to the present invention.

FIG. 3 is a circuit configuration diagram showing a configuration example of a conventional optical signal amplifier circuit.

[Explanation of symbols]

 Reference Signs List 1 input terminal 2 output terminal 3-1 first amplifying unit 3-2 second amplifying unit PD photodiode C coupling capacitance

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5J092 AA03 AA51 AA56 CA22 FA12 FA15 FA17 HA01 HA25 HA44 MA01 MA13 MA20 SA01 TA01 UL02 5J100 AA03 AA14 AA16 BA02 BB01 BB07 BB17 BC05 CA01 CA05 CA12 CA14 CA20 DA06 EA02 FA05 Q01 LA

Claims (2)

[Claims] 1. An optical information recording / reproducing apparatus for reproducing / recording / erasing by irradiating an optical information recording medium with light, comprising: a light receiving element for detecting reflected light from the medium; In the optical signal amplifier circuit that converts the photocurrent from the to the voltage, the base is connected to the input terminal,
An input comprising a first transistor having a collector connected to a first power supply, and a first resistor having one end connected to the emitter of the first transistor and the other end connected to a second power supply. A second transistor having a base connected to the emitter of the first transistor, an emitter connected to the second power supply, and a collector connected to the first power supply via a second resistor; , The base is connected to the collector of the second transistor, and the collector is connected to the first transistor.
A third transistor connected to the power supply of the third transistor, a third resistor having one end connected to the emitter of the third transistor, one end connected to the emitter of the third transistor, and the other end connected to the first transistor. A first amplifying unit composed of a first feedback resistor connected to the base of the first transistor; a base connected to the emitter of the first transistor; an emitter connected to the second power supply; A fourth transistor connected to the first power supply via a fourth resistor, and a fifth transistor having a base connected to the collector of the fourth transistor and a collector connected to the first power supply. A transistor, a fifth resistor having one end connected to the emitter of the fifth transistor, one end connected to the emitter of the fifth transistor, and the other end connected to the emitter of the first transistor. A second amplifying unit composed of the first feedback resistor connected to the first transistor and a second feedback resistor having a different resistance value; and a sixth transistor having a base connected to the base of the third transistor. A seventh transistor having a base connected to the base of the fifth transistor, and a seventh transistor having one end connected to the emitter of the sixth transistor and the other end connected to the other end of the third resistor. 6, a seventh resistor having one end connected to the emitter of the seventh transistor, the other end connected to the other end of the fifth resistor, and one end connected to the sixth transistor and the seventh resistor. An eighth resistor connected to the collector of the transistor, the other end connected to the first power supply, a base connected to one end of the eighth resistor, a collector connected to the first power supply, and an emitter Connected to the output terminal And 8 of the transistors, one end connected to said output terminal, the other end second
An output unit including a ninth resistor connected to a power supply of the first type; a first switch having one end connected to the other end of the third resistance and the other end connected to the second power source; A second switch having one end connected to the other end of the fifth resistor, the other end connected to the second power supply, and one end connected to the base of the sixth transistor, and the other end connected to the sixth transistor. A tenth resistor connected to one end of the second switch, and an eleventh resistor connected at one end to the base of the seventh transistor and the other end connected to one end of the first switch. An optical signal amplifying circuit comprising a gain switching unit. 2. The ninth switch, wherein the first switch has a collector connected to the other end of the third resistor, an emitter connected to the second power supply, and a first control signal input to a base. Wherein the second switch comprises:
A collector is connected to the other end of the fifth resistor, an emitter is connected to the second power supply, and a base is configured by a tenth transistor to which a second control signal is input. The optical signal amplifier circuit according to claim 1.