JPS6281084A - Laser diode driving circuit - Google Patents

Laser diode driving circuit

Info

Publication number
JPS6281084A
JPS6281084A JP22120585A JP22120585A JPS6281084A JP S6281084 A JPS6281084 A JP S6281084A JP 22120585 A JP22120585 A JP 22120585A JP 22120585 A JP22120585 A JP 22120585A JP S6281084 A JPS6281084 A JP S6281084A
Authority
JP
Japan
Prior art keywords
fet
circuit
laser diode
voltage
output
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP22120585A
Other languages
Japanese (ja)
Inventor
Yuji Miyaki
裕司 宮木
Takemi Endo
遠藤　竹美
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fujitsu Ltd
Original Assignee
Fujitsu Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fujitsu Ltd filed Critical Fujitsu Ltd
Priority to JP22120585A priority Critical patent/JPS6281084A/en
Publication of JPS6281084A publication Critical patent/JPS6281084A/en
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
    • H01S5/042—Electrical excitation ; Circuits therefor

Landscapes

  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Semiconductor Lasers (AREA)

Abstract

PURPOSE:To prevent the variation in output due to difference in FET characteristics such as a pinch-off voltage or transconductance and to enable a laser diode to have high-speed, stable and high output, by providing an amplitude variable amplifier circuit in the step prior to an FET circuit for supplying pulse current to the laser diode. CONSTITUTION:A minimum value of input signals is fixed to an FET pinch-off voltage by a clamp circuit 14 or the like. An input signal to an FET driving circuit 13 is previously changed in amplitude as required by an amplitude variable circuit 15 before its supplied to an ON/OFF FET gate electrode. According to this construction, if the inclination of a characteristic curve is gentle and an output current is low, the input signal can be amplified and supplied to the FET circuit 13 for providing higher output current Ip. If the inclination is steep and the output current is low, the amplification factor can be decreased for limiting the output current. Further, by amplifying the input signal, driving current can be generated, avoiding the curved portion in the characteristic curve close to the FET pinch-off point. Thus, a circuit capable of turning the emission of a laser diode ON and OFF correctly and reliably can be realized.

Description

【発明の詳細な説明】 〔概要〕 ＦＥＴを使用するレーザダイオード駆動回路において、
振幅制限用の差動増幅器を設けることによりＦＥＴの入
力信号振幅を制御し、ＦＥＴの特性バラツキを補償する
ものである。[Detailed Description of the Invention] [Summary] In a laser diode drive circuit using FET,
By providing a differential amplifier for amplitude limiting, the input signal amplitude of the FET is controlled and variations in the characteristics of the FET are compensated for.

〔産業上の利用分野〕[Industrial application field]

本発明はレーザダイオード駆動回路の改良に関する。 The present invention relates to improvements in laser diode drive circuits.

レーザダイオードを断続発光させるタメ、パルス電流が
レーザダイオードに供給される。この場合高速且つ高出
力の光パルスを得るのには、大電流を高速に開閉出来る
ＦＥＴ回路を駆動回路として使用するのが有利である。A pulse current is supplied to the laser diode to cause the laser diode to emit light intermittently. In this case, in order to obtain high-speed and high-output optical pulses, it is advantageous to use an FET circuit that can quickly open and close a large current as a drive circuit.

しかし、ＦＥＴは電気特性にバラツキがあり、レーザダ
イオードの発光動作に影響を与えるので、その改善が望
ましい。However, since FETs have variations in electrical characteristics and affect the light emission operation of the laser diode, it is desirable to improve them.

〔従来の技術〕[Conventional technology]

従来レーザダイオードを駆動する為、第４図に示すＰＥ
Ｔ使用のレーザダイオード駆動回路が用いられている。Conventionally, to drive a laser diode, the PE shown in Figure 4
A laser diode drive circuit using T is used.

これは、２個のＰＵＴ　２．３を使用し、その１個のＰ
ＥＴ　２はゲイト電極のバイアス電圧設定によって、常
時レーザダイオードへ発光闇値直下の電流を供給する電
流バイアス用として使用し、他方のＦＥＴ　３はそのゲ
イト入力電圧によって、レーザダイオードの電流を発光
闇値の上下に切替るレーザ発光のオンオフ用として使用
する。しかし、レーザダイオードの駆動に使用するＦＥ
Ｔは、特性にバラツキがあり、ピンチオフ電圧がＦＥＴ
毎に異なり、相互コンダクタンスもそれぞれ相違する。This uses two PUTs 2.3 and one PUT
ET 2 is used for current bias to constantly supply a current just below the light emission dark value to the laser diode by setting the bias voltage of the gate electrode, and the other FET 3 is used to control the current of the laser diode to the light emission dark value by setting the gate electrode bias voltage. Used to turn on/off laser emission that switches up and down. However, the FE used to drive the laser diode
T has variations in characteristics, and the pinch-off voltage is different from that of FET.
Each type is different, and the mutual conductance is also different.

従って、同一入力端子を与えた場合においても、必ずし
も常に同一の発光出力が得られるとは限らない。Therefore, even when the same input terminal is applied, the same light emission output is not always obtained.

第５図はＦＥＴのゲート入力電圧ＶＧｓと出力電流１０
ｓの関係を示す。Figure 5 shows the FET gate input voltage VGs and output current 10
This shows the relationship between s.

図においてＶｐはピンチオフ電圧で、出力電流がＯとな
るゲート電圧ＶＧｓを意味する。しかし、ＦＥＴの特性
のバラツキにより、ＶｐＯ値はＦＥＴ毎に異なる値をと
る。その結果、板金入力パルス電圧Ｖｉｎが一定振幅、
一定基準電圧値で供給されたとしても、入力パルス電圧
の０値は特性図上のピンチオフ電圧Ｖｐの位置に対し左
右へ相対的にずれることになる。ピンチオフ電圧Ｖｐが
右側へ相対的にずれる■の場合は出力パルス電流の振幅
は減少する。In the figure, Vp is a pinch-off voltage, meaning a gate voltage VGs at which the output current becomes O. However, due to variations in the characteristics of FETs, the VpO value takes different values for each FET. As a result, the sheet metal input pulse voltage Vin has a constant amplitude,
Even if a constant reference voltage value is supplied, the zero value of the input pulse voltage will be shifted left and right relative to the position of the pinch-off voltage Vp on the characteristic diagram. In the case (2) in which the pinch-off voltage Vp is relatively shifted to the right, the amplitude of the output pulse current decreases.

また逆にピンチオフ電圧Ｖｐが相対的に左側にずれる■
の場合は出力パルス電流の振幅は増大する。Conversely, the pinch-off voltage Vp shifts relatively to the left.
In this case, the amplitude of the output pulse current increases.

しかもこの際、出力パルス電流は完全にはオフとならず
人力パルス電圧０においても出力電流１ｐが流れること
になりレーザダイオードを発光させ、所謂０発光現象を
起こす。Moreover, at this time, the output pulse current is not completely turned off, and the output current 1p flows even when the human input pulse voltage is 0, causing the laser diode to emit light, causing a so-called 0 light emission phenomenon.

また、入力電圧がピンチオフ電圧Ｖｐ以下の部分で切ら
れた場合、出力パルス波形の半値幅が変化する。Furthermore, when the input voltage is cut off at a portion below the pinch-off voltage Vp, the half-width of the output pulse waveform changes.

そこで、この問題を解決する為に、スイッチング用のＦ
ＥＴのゲート入力部にツェナーダイオードを接続し、こ
れに抵抗を介してバイアス電流を流し、最小値入力電圧
値をＦＥＴのピンチオフ電圧値となるように調整する方
法が考えられる。Therefore, in order to solve this problem, the switching F
One possible method is to connect a Zener diode to the gate input portion of the ET, flow a bias current through it through a resistor, and adjust the minimum input voltage value to the pinch-off voltage value of the FET.

また、ＦＥＴの特性バラツキが大きい時は、−個のツェ
ナーダイオードだけでは調整範囲が不充分となるので、
スイッチング用のＰＥＴのゲート人力部にクランプ回路
を設ける方式も考えられる。これは、クラ、ンプ電圧の
印加されるクランプダイオード、即ち順方向電流が成る
値以上になるとき、その電圧降下を一定値に固定するダ
イオードとコンデンサからなる回路を使用し、ＦＥＴの
ピンチオフ電圧Ｖｐのバラツキに対応し、クランプ電圧
の設定値を変えるものである。Also, when there are large variations in FET characteristics, the adjustment range will be insufficient with only - Zener diodes, so
It is also conceivable to provide a clamp circuit in the gate power section of the PET for switching. This uses a clamp diode to which the clamp voltage is applied, that is, a circuit consisting of a diode and a capacitor that fixes the voltage drop to a constant value when the forward current exceeds the value. The setting value of the clamp voltage is changed in response to the variation in the voltage.

〔発明が解決しようとする問題点〕[Problem that the invention seeks to solve]

上記の様に、レーザダイオード駆動回路のＦＥＴのピン
チオフ電圧のバラツキにて生じる、入力電圧カットによ
る出力半値幅の変動、オフ信号時の残留電流による０発
光の問題はある程度解決されるが、相互コンダクタンス
のバラツキも解決する必要がある。As mentioned above, the problems of fluctuations in the output half-width due to input voltage cut and zero emission due to residual current at the off signal, which occur due to variations in the pinch-off voltage of the FET of the laser diode drive circuit, can be solved to some extent, but the mutual conductance It is also necessary to resolve the variation in

即ち、ゲイト・ソース電圧対ドレイン・ソース電流特性
曲線のバラツキは曲線の（ＩＪｉ斜に緩急を生じまたピ
ンチオフ点近傍の曲線の湾曲にも相違を与える。その結
果同一人力に対しても、各ＦＥＴによる出力電流値に大
小の相違が生じ、半値幅の変動や０発光の問題が依然と
して存在し、完全にこれが解決されないので問題である
。In other words, variations in the gate-source voltage vs. drain-source current characteristic curve cause the (IJi slope of the curve to be steeper or steeper) and also cause a difference in the curvature of the curve near the pinch-off point.As a result, even with the same human power, each FET This is a problem because the output current value differs in magnitude due to this, and the problem of half-width fluctuation and zero light emission still exists, and this problem has not been completely solved.

〔問題点を解決するための手段〕[Means for solving problems]

上記の問題点は、 パルス電流をレーザダイオード（１１）に供給するＦＥ
Ｔ回路（１３）の前段に振幅可変増幅回路（１５）を備
えてなる 本発明によるレーザダイオード駆動回路によって解決さ
れる。The above problem is caused by the FE supplying the pulse current to the laser diode (11).
This problem is solved by the laser diode drive circuit according to the present invention, which includes a variable amplitude amplifier circuit (15) at the front stage of the T circuit (13).

〔作用〕[Effect]

本発明によれば、第１図の原理図に示すように、入力信
号の最小値はクランプ回路１４等にてＦＥＴのピンチオ
フ電圧Ｖｐに固定され、ＦＥＴ駆動回路１３への入力信
号は振幅可変回路１５にて予め所望の振幅に変えてから
オンオフ用のＦＥＴのゲイト電極に供給する。この様に
すれば、第３図に示す特性曲線の傾斜が緩く出力電流が
小さくなる場合入力信号を増幅してＮＥＴ回路１３に供
給して出力電流１ｐを大■に、また傾斜が急で出力電流
ｒｐが大となる時は増幅度を下げて出力電流を抑える■
ことができる。According to the present invention, as shown in the principle diagram of FIG. In step 15, the amplitude is changed to a desired amplitude and then supplied to the gate electrode of the on/off FET. In this way, when the slope of the characteristic curve shown in FIG. When the current rp becomes large, lower the amplification degree to suppress the output current■
be able to.

更に、入力信号を増幅することにより、ＦＥＴのピンチ
オフ点に近い特性曲線の湾曲部分を避けて駆動電流を発
生することにより、レーザダイオ−ド発光のオンオフを
確実正確に行う回路が得られる。Further, by amplifying the input signal and generating the drive current while avoiding the curved portion of the characteristic curve near the pinch-off point of the FET, a circuit that reliably and accurately turns on and off the laser diode light emission can be obtained.

〔実施例〕〔Example〕

本発明の詳細を図示実施例に従い説明する。 The details of the present invention will be explained according to the illustrated embodiments.

第２図は本発明のレーザダイオード駆動回路の概略的構
成図、また第３図は本発明におけるレーザダイオード駆
動回路ＦＥＴのゲート入力電圧−出力電流特性図ある。FIG. 2 is a schematic configuration diagram of a laser diode drive circuit according to the present invention, and FIG. 3 is a gate input voltage-output current characteristic diagram of the laser diode drive circuit FET according to the present invention.

図において、１１はレーザダイオード回路、２．３はレ
ーザダイオード駆動用ＦＥＴ、４はアバランシェフォト
ダイオード、１４はクランプ回路、１５は本発明により
設けた振幅可変増幅回路、１７．１日は低域フィルター
、１９〜２２はオペＬ／　　’Ｊヨ７ア７プ、ＶＬＤＢ
　、　ＶＬＤＰ　、　ＶＦＩ３はオペレーションアンプ
の基準電圧である。In the figure, 11 is a laser diode circuit, 2.3 is a laser diode driving FET, 4 is an avalanche photodiode, 14 is a clamp circuit, 15 is a variable amplitude amplifier circuit provided according to the present invention, and 17.1 is a low-pass filter. , 19-22 is operation L/'Jyo7a7p, VLDB
, VLDP, and VFI3 are reference voltages of the operational amplifier.

データ入力信号は振幅可変増幅回路１５の入力部から、
レーザダイオード駆動回路へ供給される。The data input signal is input from the input section of the variable amplitude amplifier circuit 15.
Supplied to the laser diode drive circuit.

レーザダイオード１は駆動回路のＦＥＴ　３に与えるデ
ータ入力信号により発光し、その出力光は、アバランシ
ェフォトダイオード４により電気信号に再変換された後
、低域フィルター１８を介し直流信号としてオペレーシ
ョンアンプ１９へ入力する。The laser diode 1 emits light in response to a data input signal applied to the FET 3 of the drive circuit, and the output light is reconverted into an electric signal by the avalanche photodiode 4, and then sent to the operational amplifier 19 as a DC signal via the low-pass filter 18. input.

アンプ１９は比較回路として作用する。Amplifier 19 acts as a comparison circuit.

レーザダイオード駆動回路の入力信号は通常一定である
の′で、フィルター１７の出力直流電圧は一定である。Since the input signal to the laser diode drive circuit is normally constant, the output DC voltage of the filter 17 is constant.

しかしフィルター１８から与えられる直流電圧は駆動回
路に用いるＦＩＥＴの特性のバラツキにより一定値とな
らない。However, the DC voltage applied from the filter 18 does not have a constant value due to variations in the characteristics of the FIET used in the drive circuit.

本発明の実施例においては比較回路１９の出力信号は制
御用のオペレーションアンプ２１を介し振幅可変増幅回
路１５へ接続する。In the embodiment of the present invention, the output signal of the comparator circuit 19 is connected to the variable amplitude amplifier circuit 15 via an operational amplifier 21 for control.

今、１８の出力電圧が小になるとオペレーションアンプ
１９の出力電圧は高くなり、制御用オペレーションアン
プ２１を介し、振幅可変増幅回路１５の増幅率を高めＦ
ＥＴ　３に対する入力信号を大きくし■、レーザダイオ
ード１の光出力を大とする。Now, when the output voltage of the operational amplifier 18 becomes small, the output voltage of the operational amplifier 19 becomes high, and the amplification factor of the variable amplitude amplifier circuit 15 is increased through the operational amplifier 21 for control.
The input signal to the ET 3 is increased (2), and the optical output of the laser diode 1 is increased.

これとは逆に、フィルター１８の出力が大きくなるとオ
ペレーションアンプ１９の出力電圧は小となり、今度は
レーザダイオードｌの光出力を小にする。Conversely, when the output of the filter 18 increases, the output voltage of the operational amplifier 19 decreases, which in turn reduces the optical output of the laser diode l.

このような、ＦＥＴの特性上のバラツキによる駆動電流
の変化にもとすく先出力の変化はＶ　ＬＢＰ電圧の調整
設定によって補正される。In addition to changes in the drive current due to such variations in FET characteristics, changes in the output can be corrected by adjusting and setting the VLBP voltage.

なお、比較回路１９の出力信号はレーザダイオード１の
バイアス電流制御用のオペレーションアンプ２０を介し
、ＦＥＴ　２のゲート電極へ与えられ、レーザダイオー
ド１の光出力に応じてバイアス電流を制御する。The output signal of the comparator circuit 19 is applied to the gate electrode of the FET 2 via an operational amplifier 20 for controlling the bias current of the laser diode 1, and the bias current is controlled according to the optical output of the laser diode 1.

更に、バイアス電流制御用オペレーションアンプ２０の
出力信号はクランプレベル制御用のオペレーションアン
プ２２にも供給される。Furthermore, the output signal of the operational amplifier 20 for bias current control is also supplied to the operational amplifier 22 for clamp level control.

オペレーションアンプ２２の出力信号はクランプ回路１
４ヘクランプ電圧を供給する。クランプ電圧は、ＦＥＴ
　３の特性に応じてＶＦＢの値を定めることにより、入
力電圧がＯであるとき、ゲート電圧がピンチオフ電圧に
なる様に調整される。The output signal of the operational amplifier 22 is sent to the clamp circuit 1.
4. Supply clamp voltage. Clamp voltage is FET
By determining the value of VFB according to the characteristics of No. 3, the gate voltage is adjusted to the pinch-off voltage when the input voltage is O.

〔発明の効果〕〔Effect of the invention〕

本発明によれば、ピンチオフ電圧あるいは相互コンダク
タンス等ＦＥＴ特性のばらつきによる出力変化を防ぎ、
高速高出力の安定な光出力を発生するレーザダイオード
駆動回路を提供するものでありその作用効果は極めて大
きい。According to the present invention, output changes due to variations in FET characteristics such as pinch-off voltage or mutual conductance are prevented,
This invention provides a laser diode drive circuit that generates high-speed, high-output, and stable optical output, and its effects are extremely large.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は本発明のレーザダイオード駆動回路の原理図、 第２図は本発明のレーザダイオード駆動回路の一実施例
における概略的構成図、 第３図は本発明に於けるレーザダイオード駆動回路ＦＥ
Ｔのゲート入力電圧−出力電 流特性図、 第４図は従来のＰＵＴ使用のレーザダイオード駆動回路
、 第５図はＦＥＴのゲート入力電圧−出力電流特性図であ
る。 図において、 １はレーザダイオード、 ２．３はＦＥＴ　。 ４はアバランシェフォトダイオード、 １１はレーザダイオード回路、 ｌ２は制御回路、 １３はＦＥＴ回路、 １４はクランプ回路、 １５は振幅可変増幅回路、 １７．１８は低域フィルター、 １９〜２２はオペレーションアンプである。Fig. 1 is a principle diagram of a laser diode drive circuit of the present invention, Fig. 2 is a schematic configuration diagram of an embodiment of the laser diode drive circuit of the present invention, and Fig. 3 is a diagram of the laser diode drive circuit FE in the present invention.
FIG. 4 shows a conventional laser diode drive circuit using a PUT, and FIG. 5 shows a gate input voltage-output current characteristic diagram of an FET. In the figure, 1 is a laser diode, and 2.3 is an FET. 4 is an avalanche photodiode, 11 is a laser diode circuit, l2 is a control circuit, 13 is an FET circuit, 14 is a clamp circuit, 15 is a variable amplitude amplifier circuit, 17.18 is a low-pass filter, and 19 to 22 are operational amplifiers. .

Claims (1)

【特許請求の範囲】[Claims] パルス電流をレーザダイオード（１１）に供給するＦＥ
Ｔ回路（１３）の前段に、振幅可変増幅回路（１５）を
備えてなることを特徴とするレーザダイオード駆動回路
。FE that supplies pulsed current to the laser diode (11)
A laser diode drive circuit comprising a variable amplitude amplifier circuit (15) at the front stage of a T circuit (13).
JP22120585A 1985-10-04 1985-10-04 Laser diode driving circuit Pending JPS6281084A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP22120585A JPS6281084A (en) 1985-10-04 1985-10-04 Laser diode driving circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP22120585A JPS6281084A (en) 1985-10-04 1985-10-04 Laser diode driving circuit

Publications (1)

Publication Number Publication Date
JPS6281084A true JPS6281084A (en) 1987-04-14

Family

ID=16763110

Family Applications (1)

Application Number Title Priority Date Filing Date
JP22120585A Pending JPS6281084A (en) 1985-10-04 1985-10-04 Laser diode driving circuit

Country Status (1)

Country Link
JP (1) JPS6281084A (en)

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