LB1005 Operating Manual Detailed Operation
Bookham Revision 1 15
The design of the P-I filter minimizes transient behaviors when switching
between corner values. Under most circumstances, switching corner frequencies
can be performed without losing lock, which aids in searching for optimal
operation. However, the gain change when switching in and out of Int mode is
fairly large, and re-locking will typically be necessary to use the integrator-only
mode.
The Acquire toggle switch controls the output of the filter section:
• Lock Off: The integrator is reset. The control voltage is zero.
• LFGL: The P-I filter output is enabled, but the low frequency gain is limited
according to the LF Gain Limit switch. This mode is useful for acquiring lock
and situations where limiting the DC gain is necessary.
• Lock On: The integrator of the P-I filter is fully enabled. The LF Gain Limit
is disabled.
The LB1005 operating bandwidth refers to the frequency where the proportional
gain falls off by 3 dB. The filter functions specified in Figure 8 are guaranteed to
the minimum specified bandwidth of 10 MHz. Behavior of the filter response
beyond this frequency is unspecified.
Setting Output Voltage Limits
The positive and negative voltage limits of the LB1005 Output can be
independently adjusted with the Output Voltage Limit trimpots located on the
rear panel. The following procedure can be used to set the output voltage limits:
1. To set the positive (negative) limit, turn the Sweep Center (Output
Offset) knob fully clockwise (counter-clockwise). The Output signal
should now be at the positive (negative) voltage limit.
2. Monitoring the Output voltage on an oscilloscope or voltmeter, turn the
+ (-) trimpot on the rear panel until the desired positive (negative)
output limit voltage is reached. Clockwise adjustment of these trimpots
results in a more positive voltage.
When adjusting both output voltage limits, specified operation only occurs if the
voltage difference between the negative and positive limits is greater than 2 V.
Unspecified behavior occurs if this condition is violated.
The total 10-turn range of the Sweep Center knob is automatically adjusted to
correspond to the full output voltage range as determined by the positive and
negative output voltage limits.
Warning: Carefully measure output voltages from the LB1005 before connecting to a
device that can be damaged by overvoltage.
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