Abstract: A multi-layer structured printed circuit substrate having an upper conductive layer and a lower conductive layer with an inter-layer insulating layer is used. A chip assembly part of bump connection type is formed by forming openings in a portion of the upper conductive layer and the inter-layer insulating layer in order to expose the lower conductive layer. A bear chip is buried in the chip assembly part for assembly. A sealing member is filled in the lower space of the bear chip. A flat plate type radiating plate having an opening corresponding to the chip assembly part is located on the substrate and a heat conductive adhesive is filled between the radiating plate and the bear chip.

Abstract: A bias circuit accurately compensates temperature coefficient of an optical multiplication in an avalanche photodiode with low power consumption. Temperature coefficient voltage for compensating temperature coefficient of the multiplication of the photodiode is delivered from an emitter follower added a constant voltage to an input of an operational amplifier. The output of the operational amplifier is added, via a voltage regulating diode, to a base of a transistor of which emitter and collector are respectively connected to a terminal of the photodiode and a negative power source. Emitter voltage of the transistor is dividedly connected to another input terminal of the operational amplifier, wherein this connection is negative feedback. The temperature coefficient voltage generated at the emitter follower is amplified inversely proportional to the divided ratio of the emitter voltage of the transistor in order to compensate the temperature coefficient of the multiplication of the photodiode.

Abstract: In an amplifier including an AC amplifier, its operation level shifts according to input waveforms. When a positive input signal is, for example, inputted, the circuit feeds out a synthesized signal to the amplifier in which signal a positive and negative portions are symmetry and have a time difference. The circuit compensates an operating level of the amplifier so that it amplifies a small signal to keep always a zero level of the signal being constant in spite of various signal waveforms and amplitudes whereby a linearity of the amplifier is improved and fluctuations of a dynamic range thereof are eliminated.