The present disclosure includes circuits and methods for power amplifiers. The elongated member has an outer diameter which enables it to be inserted into and through an accessory channel of an endoscope to view the human or animal tissue or material to be treated with infrared radiation. The control unit is configured to control the at least one application device to electrically inject at least one examination signal into the conductive tracks. Said fluorescent powder is of silicate series. In addition, air flow moving toward the disk pack may be contracted to allow efficient energy conversion from pressure energy to kinetic energy prior to merging of the bypass air flow with the air flow among the disks.