An electronic probe circuit having ac and dc amplifiers and an input compensation subcircuit is enclosed within a trim housing that replicates the electrical effect of the probe housing. The circuit is laser trimmed through ports in the trim housing. The difference between the voltage at 80 nsec and...http://www.google.de/patents/US5420515?utm_source=gb-gplus-sharePatent US5420515 - Active circuit trimming with AC and DC response trims relative to a known response
