Abstract: A voltage generation circuit includes a control circuit which outputs a first digital signal, a DAC which outputs a first analog signal corresponding to the first digital signal, and an attenuator which is connected to an output terminal of the DAC and is configured to output a voltage signal obtained by attenuating the first analog signal input from the DAC.

Abstract: A harmonic rejection mixer is disclosed that is capable of supporting wideband reception without any increase in circuit area. In this apparatus, transistors convert an RF signal to currents. Transistors perform frequency conversion based on the currents from the transistors and local oscillation signals. Transistors distribute the currents from the transistors to all transistors or some transistors based on a predetermined ratio. A load adds up the currents from the transistors and converts the resultant current to a voltage.

Abstract: The ramp-signal generator circuit includes a reference voltage generator that changes the voltage of a reference signal Vr to a comparator setting voltage VR for compensating for a voltage difference between a reference signal Vr and an analog input signal (Vs1-Vsn) before comparison by an analog-to-digital converter circuit and outputs a ramp signal whose slope starts from the comparator setting voltage VR in response to a start of the comparison. The ramp-signal generator circuit is configured to add a predetermined enhanced voltage VA to the comparator setting voltage VR before the comparison.

Abstract: A harmonic rejection mixer is disclosed that is capable of supporting wideband reception without any increase in circuit area. In this apparatus, transistors convert an RF signal to currents. Transistors perform frequency conversion based on the currents from the transistors and local oscillation signals. Transistors distribute the currents from the transistors to all transistors or some transistors based on a predetermined ratio. A load adds up the currents from the transistors and converts the resultant current to a voltage.

Abstract: The ramp-signal generator circuit includes a reference voltage generator that changes the voltage of a reference signal Vr to a comparator setting voltage VR for compensating for a voltage difference between a reference signal Vr and an analog input signal (Vs1-Vsn) before comparison by an analog-to-digital converter circuit and outputs a ramp signal whose slope starts from the comparator setting voltage VR in response to a start of the comparison. The ramp-signal generator circuit is configured to add a predetermined enhanced voltage VA to the comparator setting voltage VR before the comparison.

Abstract: A voltage generation circuit includes a control circuit which outputs a first digital signal, a DAC which outputs a first analog signal corresponding to the first digital signal, and an attenuator which is connected to an output terminal of the DAC and is configured to output a voltage signal obtained by attenuating the first analog signal input from the DAC.

Abstract: A ramp wave output circuit includes a ramp wave generation circuit generating a ramp wave, and a low-pass filter having a variable cutoff frequency, which receives the ramp wave. The low-pass filter operates at a first cutoff frequency for a predetermined time period after the receipt of the ramp wave, and at a second cutoff frequency, which is larger than the first cutoff frequency, after the predetermined time period has passed.

Abstract: A resistor-ladder voltage generator circuit is provided, which controls so that k switches among consecutive (k+1) switches out of a plurality of switches connected to the resistor ladder circuit are simultaneously set to an ON state, and which temporally switches the value of k. This allows voltage waveforms having different slopes to be arbitrarily obtained, ranging from a voltage waveform having a small slope to a voltage waveform having a large slope, thereby improving the resolution of a generated voltage waveform without increasing the numbers of resistors and switches, while A/D conversion time is not increased even if the number of bits is increased. In addition, by using this voltage generator circuit as a ramp generator circuit, and by dynamically switching the slope of the ramp wave, acceleration of an image sensor is achieved.

Abstract: A resistor-ladder voltage generator circuit is provided, which controls so that k switches among consecutive (k+1) switches out of a plurality of switches connected to the resistor ladder circuit are simultaneously set to an ON state, and which temporally switches the value of k. This allows voltage waveforms having different slopes to be arbitrarily obtained, ranging from a voltage waveform having a small slope to a voltage waveform having a large slope, thereby improving the resolution of a generated voltage waveform without increasing the numbers of resistors and switches, while A/D conversion time is not increased even if the number of bits is increased. In addition, by using this voltage generator circuit as a ramp generator circuit, and by dynamically switching the slope of the ramp wave, acceleration of an image sensor is achieved.

Abstract: A ramp wave output circuit includes a ramp wave generation circuit generating a ramp wave, and a low-pass filter having a variable cutoff frequency, which receives the ramp wave. The low-pass filter operates at a first cutoff frequency for a predetermined time period after the receipt of the ramp wave, and at a second cutoff frequency, which is larger than the first cutoff frequency, after the predetermined time period has passed.

Abstract: A ladder resistor circuit generates a plurality of different reference voltages. A plurality of switching circuits correspond to a plurality of taps of the ladder resistor circuit. Each of the plurality of switching circuits is connected at one end to a corresponding one of the taps and connected at the other end to an output node, and has a variable on-resistance value. A control circuit selects continuous n (where n is any integer equal to or greater than 2) of the plurality of switching circuits, turns the n switching circuits on, and sets the respective on-resistance values of the n switching circuits.

Abstract: The communication performance of a radio communication system is improved while keeping short time necessary for attaining synchronization. A low noise amplifier is selectively provided with one of an input signal supplied from the outside of the system and an oscillation output signal of a local oscillator. A mixer integrates the oscillation output signal of the local oscillator and an output signal of the low noise amplifier. An intensity discriminating unit discriminates the signal intensity of an output of the mixer. In a first state, the low noise amplifier amplifies the oscillation output signal of the local oscillator, and a control unit learns a frequency band of the low noise amplifier for maximizing the signal intensity on the basis of the discrimination result of the intensity discriminating unit. In a second state, the low noise amplifier is set to the frequency band learned in the first state and amplifies the input signal.

Abstract: A ladder resistor circuit generates a plurality of different reference voltages. A plurality of switching circuits correspond to a plurality of taps of the ladder resistor circuit. Each of the plurality of switching circuits is connected at one end to a corresponding one of the taps and connected at the other end to an output node, and has a variable on-resistance value. A control circuit selects continuous n (where n is any integer equal to or greater than 2) of the plurality of switching circuits, turns the n switching circuits on, and sets the respective on-resistance values of the n switching circuits.

Abstract: A capacitor having a capacitance value corresponding to the size of an output current generating transistor is connected between the gate terminal of the output current generating transistor and the input terminal of an inverter circuit.

Abstract: The communication performance of a radio communication system is improved while keeping short time necessary for attaining synchronization. A low noise amplifier is selectively provided with one of an input signal supplied from the outside of the system and an oscillation output signal of a local oscillator. A mixer integrates the oscillation output signal of the local oscillator and an output signal of the low noise amplifier. An intensity discriminating unit discriminates the signal intensity of an output of the mixer. In a first state, the low noise amplifier amplifies the oscillation output signal of the local oscillator, and a control unit learns a frequency band of the low noise amplifier for maximizing the signal intensity on the basis of the discrimination result of the intensity discriminating unit. In a second state, the low noise amplifier is set to the frequency band learned in the first state and amplifies the input signal.

Abstract: A capacitor having a capacitance value corresponding to the size of an output current generating transistor is connected between the gate terminal of the output current generating transistor and the input terminal of an inverter circuit.