3.
SPECIAL GUIDANCE FOR NON-DLVA APPLICATIONS
For applications which do not involve the use of microwave detectors, i.e. where a video pulse is
to be logged, the input amp must be used in the inverting mode for negative input pulses, and in
the non- inverting configuration for positive inputs.
Measuring the log transfer function requires some care, and can be accomplished by applying a
DC level at the input and measuring the input and output voltages simultaneously. Care should be
taken to place the ground lead of the meters on the board, and not at the power-supply ground,
because there is a ground current which will lead to errors if the meters are not grounded
appropriately.
The current of L6 may need to be adjusted to optimize the linearity of the log transfer function if
this is high in the region where L6 is active. To do this, in place of R110 install a pot connected to
ground, and adjust to smooth the transfer function.
Note that if a pulse generator is used, a long tail on the output pulse is almost invariably seen.
This is not caused by the amplifier, but is a reflection on the cleanliness of the output from
available pulsers. Almost all pulsers produce tails at the 0.1% level. Producing a really clean
pulse in order to check the inherent amplifier recovery properties is not a trivial exercise. There
are methods using switched Schottky bridges which can be found in the literature.
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