可视激光驱动器有数字控制功率调制-Visible-Laser
abstract: the circuit in the figure below includes a 10-bit digital-to-analog converter (dac) with 3-wire serial input that operates and maintains a visible-light laser diode at constant average optical output power. a separate digital input line (mod) enables a comparator with open-drain output (ic4) to implement digital communications by pulsing the laser-diode through q1.
many laser diodes include a photodiode that generates a current proportional to the intensity (optical power) of the laser beam. most of these photodiodes, however, have relatively slow response times and cannot track the peak optical power of a typical modulated laser diode. instead, the driver circuits for these devices control the laser by monitoring a relative average optical power.
the circuit in the figure below includes a 10-bit digital-to-analog converter (dac) with 3-wire serial input that operates and maintains a visible-light laser diode at constant average optical output power. a separate digital input line (mod) enables a comparator with open-drain output (ic4) to implement digital communications by pulsing the laser-diode through q1. circuit components were chosen to minimize the layout are and cost.
for larger image
this circuit provides digital control of the modulation and power output of a visible-light laser diode.
resistor r6 converts the photodiode current to a usable voltage, which is applied to the inverting input of a leaky integrator based on the high-speed op amp ic3. the integrator smoothes out variations in the modulation and prevents the feedback loop from trying to regulate the laser pulses. the integrator is made leaky (by r10) to ensure compensation of downward as well as upward variations in the average power.
thus, the integrator creates an error signal and base drive for q1 by monitoring the voltage across r6 and comparing it to the dac's preset voltage. the dac's reference voltage (from ic1) is 2.5v, but its output-voltage buffer has a gain of 2v/v, giving the dac output an adjustment range of 0 to 5v. with its nominal base voltage set by the dac output, q1 controls the optical power by regulating current through the laser diode.
r9 provides isolation and helps to stabilize ic3 when the base of q1 is being shorted and released by a signal from the mod input. by maintaining a small laser-diode current during the off periods of digital modulation, r1 preempts another problem: startup time for a laser diode increases tremendously if the forward current goes to zero. r1 ensures that the laser current is below the threshold for lasing, but high enough to allow an acceptable turn-on time for communication and modulation.
a similar version of this article appeared in the march 23, 1998 issue of electronic design magazine.
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many laser diodes include a photodiode that generates a current proportional to the intensity (optical power) of the laser beam. most of these photodiodes, however, have relatively slow response times and cannot track the peak optical power of a typical modulated laser diode. instead, the driver circuits for these devices control the laser by monitoring a relative average optical power.
the circuit in the figure below includes a 10-bit digital-to-analog converter (dac) with 3-wire serial input that operates and maintains a visible-light laser diode at constant average optical output power. a separate digital input line (mod) enables a comparator with open-drain output (ic4) to implement digital communications by pulsing the laser-diode through q1. circuit components were chosen to minimize the layout are and cost.
for larger image
this circuit provides digital control of the modulation and power output of a visible-light laser diode.
resistor r6 converts the photodiode current to a usable voltage, which is applied to the inverting input of a leaky integrator based on the high-speed op amp ic3. the integrator smoothes out variations in the modulation and prevents the feedback loop from trying to regulate the laser pulses. the integrator is made leaky (by r10) to ensure compensation of downward as well as upward variations in the average power.
thus, the integrator creates an error signal and base drive for q1 by monitoring the voltage across r6 and comparing it to the dac's preset voltage. the dac's reference voltage (from ic1) is 2.5v, but its output-voltage buffer has a gain of 2v/v, giving the dac output an adjustment range of 0 to 5v. with its nominal base voltage set by the dac output, q1 controls the optical power by regulating current through the laser diode.
r9 provides isolation and helps to stabilize ic3 when the base of q1 is being shorted and released by a signal from the mod input. by maintaining a small laser-diode current during the off periods of digital modulation, r1 preempts another problem: startup time for a laser diode increases tremendously if the forward current goes to zero. r1 ensures that the laser current is below the threshold for lasing, but high enough to allow an acceptable turn-on time for communication and modulation.
a similar version of this article appeared in the march 23, 1998 issue of electronic design magazine.
nova6可以升级鸿蒙吗 华为鸿蒙第二波公测开启
金立倒闭原因或在董事长刘立荣身上 富士康再回应缩减成本和裁员
Atmel联手华硕，XSense技术拳拳助力CES 2013
爱特梅尔发布基于Cortex-M4的快闪微控制器SAM4S16
电快速脉冲对设备影响的原因,针对电源线的措施
可视激光驱动器有数字控制功率调制-Visible-Laser
语音电路报读电路的设计方法及在火控系统中的应用
实用模拟电路小常识浅析
窥探下一波半导体产业并购主要战场
蓝牙耳机哪款音质好？2020最受欢迎十大蓝牙耳机品牌
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Order 66实验室为VR产品“intervention onville”募集资金4万美元
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AMS1117稳压电路图（1.2v、1.8v、3.3v、5v）
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