Abstract: Each of varicaps 50A to 50C configured to be connected in parallel is an MOS capacitor III produced under a common and single process condition. Each of the varicaps 50A to 50C has a conductor layer serving as a second electrode and formed via a capacitance insulating film on a first conductivity-type semiconductor substrate serving as a first electrode, and a second conductivity-type impurity region formed near a surface in proximity to a region of the first conductivity-type semiconductor substrate opposing the conductor layer. Each of the varicaps 50A to 50C is configured such that a capacitance value as a capacitance element between the first conductivity-type semiconductor substrate serving as the first electrode and the conductor layer serving as the second electrode is changed by applying a control voltage to the conductor layer while applying any one of a plurality of types of direct-current voltages having different voltages to the second conductivity-type impurity region.

Abstract: Each of varicaps 50A to 50C configured to be connected in parallel is an MOS capacitor III produced under a common and single process condition. Each of the varicaps 50A to 50C has a conductor layer serving as a second electrode and formed via a capacitance insulating film on a first conductivity-type semiconductor substrate serving as a first electrode, and a second conductivity-type impurity region formed near a surface in proximity to a region of the first conductivity-type semiconductor substrate opposing the conductor layer. Each of the varicaps 50A to 50C is configured such that a capacitance value as a capacitance element between the first conductivity-type semiconductor substrate serving as the first electrode and the conductor layer serving as the second electrode is changed by applying a control voltage to the conductor layer while applying any one of a plurality of types of direct-current voltages having different voltages to the second conductivity-type impurity region.

Abstract: A voltage regulator comprises an N type depletion MOS transistor having a drain connected to the positive electrode side of a power supply, a source connected to a stabilizing capacitor, and a gate receiving a constant reference voltage, and has an output terminal at the source of the N type depletion MOS transistor. In this simple circuit configuration, the voltage regulator can markedly reduce a noise carried on an output voltage.

Abstract: A nonvolatile memory cell includes: a first NMOS transistor having a floating gate; a second NMOS transistor and a third NMOS transistor connected to a drain side and a source side of the first NMOS transistor; and a first PMOS transistor and a second PMOS transistor each having the floating gate as a gate, and wherein a read signal is inputted to gates of the second and third NMOS transistors, a control gate signal is inputted to a source and an n-well of the first PMOS transistor, an erase signal is inputted to a source and an n-well of the second PMOS transistor, and a write data signal is inputted to a source of the first NMOS transistor.

Abstract: A nonvolatile memory cell, comprising: a first NMOS transistor having a floating gate; a second NMOS transistor and a third NMOS transistor connected to a drain side and a source side of the first NMOS transistor; and a first PMOS transistor and a second PMOS transistor each having the floating gate as a gate, and wherein a read signal is inputted to gates of the second and third NMOS transistors, a control gate signal is inputted to a source and an n-well of the first PMOS transistor, an erase signal is inputted to a source and an n-well of the second PMOS transistor, and a write data signal is inputted to a source of the first NMOS transistor.

Abstract: An AC amplifier has an amplification circuit, and a bias circuit connected together by connecting wiring. The bias circuit receives an input of an AC signal from the amplification circuit via the connecting wiring. A DC voltage of the bias circuit conformed to the amplitude of the AC signal of the amplification circuit is supplied to the amplification circuit via the connecting wiring.

Abstract: A bypass capacitance is connected to a node between first and second self-bias resistances connected in series between an input and an output of an inverter. The bypass capacitance accommodates changes in the output voltage of the inverter to suppress the feedback effect from the output side to the input side of the inverter. That is, the bypass capacitance plays the role of suppressing a decrease in the input impedance by the Miller effect.

Abstract: An AC amplifier has an amplification circuit, and a bias circuit connected together by connecting wiring. The bias circuit receives an input of an AC signal from the amplification circuit via the connecting wiring. A DC voltage of the bias circuit conformed to the amplitude of the AC signal of the amplification circuit is supplied to the amplification circuit via the connecting wiring.

Abstract: A MOS-type capacitor includes a semiconductor substrate of a first conductive type serving as a first electrode, a conductor layer formed on the semiconductor substrate via a capacitive insulation film and serving as a second electrode, and an impurity region of a second conductive type formed in the vicinity of the surface of the semiconductor substrate at a location in proximity to a region facing the conductor layer. The MOS-type capacitor is used as a variable capacitor in a VCO (voltage-controlled oscillator) having a widened frequency range.