Abstract: When an external clock signal exceeding a power supply voltage is input to a first terminal, a voltage of a bulk of a P type MOS transistor becomes higher than a power supply voltage, but a current does not flow from the bulk of the P type MOS transistor to a first power supply line since a first diode is provided in a forward direction with respect to a direction of a current flowing from a first power supply line to the bulk of the P type MOS transistor. Therefore, it is possible to reliably prevent a reverse current from flowing from the first terminal to the first power supply line.

Abstract: A protection circuit includes a power supply terminal, a ground terminal, a control unit connected to the power supply terminal and the ground terminal, and a supply unit connected to the power supply terminal and the ground terminal, for preventing application of voltage in a reverse direction to a circuit unit having a predetermined function. In this case, the control unit generates a control potential, which controls the control unit and the supply unit in accordance with a potential supplied from the power supply terminal and a potential supplied from the ground terminal. The supply unit is configured to be capable of supplying current to a circuit unit connected to a subsequent stage on the basis of a potential supplied from the power supply terminal, a potential supplied from the ground terminal, and the control potential generated by the control unit.

Abstract: A protection circuit includes a power supply terminal, a ground terminal, a control unit connected to the power supply terminal and the ground terminal, and a supply unit connected to the power supply terminal and the ground terminal, for preventing application of voltage in a reverse direction to a circuit unit having a predetermined function. In this case, the control unit generates a control potential, which controls the control unit and the supply unit in accordance with a potential supplied from the power supply terminal and a potential supplied from the ground terminal. The supply unit is configured to be capable of supplying current to a circuit unit connected to a subsequent stage on the basis of a potential supplied from the power supply terminal, a potential supplied from the ground terminal, and the control potential generated by the control unit.

Abstract: An operational amplification circuit includes a differential amplification circuit portion that amplifies a differential input, and an output circuit portion that outputs the amplified output using a signal amplified in the differential amplification circuit portion. The differential amplification circuit portion is provided with a pair of first transistors to which signals are differentially input, and second and third transistors which are connected to current paths of the pair of first transistors and which constitute current mirror circuits with respect to each other. The output circuit portion is provided with a fourth transistor, a gate of which is connected to a drain of the second transistor, and an amplified output is output from a drain of the fourth transistor.

Abstract: An operational amplification circuit includes a differential amplification circuit portion that amplifies a differential input, and an output circuit portion that outputs the amplified output using a signal amplified in the differential amplification circuit portion. The differential amplification circuit portion is provided with a pair of first transistors to which signals are differentially input, and second and third transistors which are connected to current paths of the pair of first transistors and which constitute current mirror circuits with respect to each other. The output circuit portion is provided with a fourth transistor, a gate of which is connected to a drain of the second transistor, and an amplified output is output from a drain of the fourth transistor.

Abstract: A direct conversion tuner includes mixers that orthogonally convert a digital television signal located in high channels of the VHF band and a digital television signal located in a frequency range of 470 MHz to 608 MHz in the UHF band directly into baseband signals, and an oscillator that supplies local oscillation signals to the mixers. The oscillator is caused to oscillate at a frequency that is sixfold a frequency in the high channels of the VHF band or a frequency that is twofold a frequency in the frequency range of 470 MHz to 608 MHz in the UHF band. An oscillation signal having the twofold frequency is divided by two and an oscillation signal having the sixfold frequency is divided by six to generate local oscillation signals having orthogonal phases for both of these oscillation signals. The local oscillation signals having the divided frequencies are supplied to the mixers.

Abstract: A direct conversion tuner includes mixers that orthogonally convert a digital television signal located in high channels of the VHF band and a digital television signal located in a frequency range of 470 MHz to 608 MHz in the UHF band directly into baseband signals, and an oscillator that supplies local oscillation signals to the mixers. The oscillator is caused to oscillate at a frequency that is sixfold a frequency in the high channels of the VHF band or a frequency that is twofold a frequency in the frequency range of 470 MHz to 608 MHz in the UHF band. An oscillation signal having the twofold frequency is divided by two and an oscillation signal having the sixfold frequency is divided by six to generate local oscillation signals having orthogonal phases for both of these oscillation signals. The local oscillation signals having the divided frequencies are supplied to the mixers.

Abstract: A multi-band oscillator includes plural pairs of oscillation transistors, which are differentially connected and which are provided independently for each oscillation frequency band; and feedback capacitor elements that connect the mutual collector and base of each pair of the oscillation transistors. The collectors of one of each pair of the oscillation transistors are connected to one another, and the collectors of the other pairs of the oscillation transistors are connected to each other. Between the collector of one of the oscillation transistors and the collector of the other oscillation transistor, a plurality of capacitor elements for switching the oscillation frequency band are connected via switching devices connected in series thereto in such a manner as to correspond to each pair of oscillation transistors, and only one pair of oscillation transistors corresponding to the capacitor element which is connected to the switching device which is turned on are placed in an operating condition.