An at least second-order active filter circuit includes an operational amplifier whose frequency response, in conjunction with an RC network, serves to set a predetermined low-pass characteristic. The two manifolds, lands and outlets may be the same or different, respectively. The second layer includes iridium. The foils are sintered to the inner wall of the casing and define a multi-channel structure for the working fluid to flow from a condensing section to an evaporating section of the heat pipe. A donor wafer is placed in contact with the first and second areas.