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Analog Technologies

ATLS100MA103

Low Noise Constant Current Laser Controller

To Avoid Output Current Distortions

The laser diode’s forward voltage and current has a non-

linear relationship shown in Figure 9.1 and 9.2. It can be

seen that when the current is low, the voltage is uncertain, it

can be between 0V to 1V or more. Thus, when setting the

output current to zero, the output voltage will oscillate

between 0V to about 1V or 1.5V, depending on the

wavelength of the laser diode. If we set the lowest output

current to a non-zero value, such as 1/10 of the laser’s

operating current but lower than the laser’s threshold current,

the laser’s optical beam can still be cut

−off, but the output

voltage will not oscillate, thus the output current will not

have distortions. The status of the LIO is similar as the

Figure 10 shown without output current distortions.

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