Abstract: A personal computer including a bottomed case, a keyboard, a top cover forming with said keyboard, an upper face covering said bottomed case, and a heat dissipation structure disposed between the upper face and the bottomed case. The heat dissipation structure includes a printed circuit board having a current consuming device mounted thereon, a first heat dissipation plate disposed under the keyboard, and a first heat conductive block coupled to the first heat dissipation plate and the printed circuit board. The heat conductive block conducts heat generated by the current consuming device to the first heat dissipation plate. The heat dissipation structure further includes a second heat dissipation plate disposed on the bottomed case, and a second heat conductive block coupled to the second heat dissipation plate and the printed board, wherein the second heat conductive block conducts the heat generated by the current consuming device to the second heat dissipation plate.

Abstract: A personal computer comprises a heat dissipation plate installed on a floor of its case, a motherboard disposed apart from the heat dissipation plate by a predetermined distance, and a daughter board disposed in such a manner that the motherboard is positioned between the heat dissipation plate and the daughter board. The daughter board is mounted with a central processing unit which generates heat. The motherboard is provided with a hole. A heat dissipation block extends from the heat dissipation plate through the hole in the motherboard, and is connected to the central processing unit through a heat conductive coupler. This forms a heat dissipation path which passes through the central processing unit, the heat dissipation block, the heat dissipation plate, and the case.

Abstract: A personal computer comprises a heat dissipation plate installed on a floor of its case, a motherboard disposed apart from the heat dissipation plate by a predetermined distance, and a daughter board disposed in such a manner that the motherboard is positioned between the heat dissipation plate and the daughter board. The daughter board is mounted with a central processing unit which generates heat. The motherboard is provided with a hole. A heat dissipation block extends from the heat dissipation plate through the hole in the motherboard, and is connected to the central processing unit through a heat conductive coupler. This forms a heat dissipation path which passes through the central processing unit, the heat dissipation block, the heat dissipation plate, and the case.

Abstract: The output signal of an l-f (low-frequency) power amplifier is supplied to an electroacoustic transducer, through an inductive element for preventing parasitic oscillation, to cause the inductive element to generate a magnetic flux whose density depends on the output current signal of the power amplifier while a current according to the magnitude of the output voltage signal of the power amplifier is supplied to the current input terminals of a Hall-effect element disposed in the magnetic field induced by the inductive element, so that a voltage according to the output power of the l-f power amplifier is taken out of the output terminals of the Hall-effect element. When the voltage exceeds a predetermined level, the l-f signal supplied to the electroacoustic transducer is attenuated by a signal attenuating circuit so that the transducer is prevented from being damaged.

Abstract: A transistor differential amplifier circuit includes a pair of NPN type amplifying transistors operated by a constant current source commonly connected to their emitters, and a pair of PNP type load transistors inserted in the collector circuits of said amplifying transistors, respectively. The load transistors are commonly biased with a constant voltage to operate within their saturation regions when input signals supplied on respective bases of the amplifying transistors are balanced, whereby pulse signals with a controlled duty ratio are obtained from the respective collectors of the amplifying transistors.