C10910 INSTRUCTION MANUAL Ver.1.19E
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If you can view the trigger signal on the oscilloscope, then setup is complete. The
final adjustment to the input light intensity is made by adjusting the ND filter while
viewing the streak image. A variable ND filter will prove convenient for adjusting the
light intensity as fine as possible at this time.
(3) Adjusting the bias current
The bias current on the C1808-03 is set to the optimal value prior to shipping. If the
output waveform becomes unstable over time, then adjust by using the following
method.
Connect a power supply and observe the C1808-03 output on an oscilloscope
(having a bandwidth of 200 MHz or higher) while the incident light is removed. Turn
the bias adjustment trimmer shown in the figure below. Turning it clockwise will
increase the bias current and a self-oscillation waveform can be seen on the
oscilloscope. Now turn the trimmer counterclockwise slowly. Turning the trimmer from
one-third to one-half a turn from the point where self-oscillation disappears will give
the point with the smallest jitter. However, if this point is too close to the
self-oscillation point, then self-oscillation may sometimes occur as the drift due to
temperature variations, so use caution. Moreover, if the bias current is set too low,
jitter may increase or a drop in trigger sensitivity may occur.
TRIG OUT
24 V IN
PIN DIODE HEAD C1808
Volume for adjustment of bias current
