Abstract: A current supply circuit supplies a bias current to operational amplifiers which constitute a pipelined AD converter. A current switching circuit switches between output currents in response to a current control signal from current control means, thereby switching between currents to be supplied from a bias circuit to the operational amplifiers via transistors. A sufficiently large current enough for the amplifiers to operate at a high frequency is supplied, while the current is switched to a lower supply current for the amplifier to operate at lower frequencies.

Abstract: A cyclic AD converter having a conversion processing speed or conversion accuracy designed no higher than necessary. In the AD converter, an input analog signal is held by a sample-and-hold circuit, and converted into a digital value by an AD conversion circuit. A DA conversion circuit converts the digital value output from the AD conversion circuit into an analog value. A subtractor circuit outputs the difference between the analog value output from the AD conversion circuit and the analog value held in the sample-and-hold circuit. An amplifier circuit amplifies the output of the subtractor circuit, and feeds back the resultant to the sample-and-hold circuit and the AD conversion circuit. In the course of this feedback-based cyclic processing, an amplification control circuit changes the gain of the amplifier circuit in accordance with the progress of the circulation.

Abstract: A current supply circuit supplies a bias current to operational amplifiers which constitute a pipelined AD converter. A current switching circuit switches between output currents in response to a current control signal from current control means, thereby switching between currents to be supplied from a bias circuit to the operational amplifiers via transistors. A sufficiently large current enough for the amplifiers to operate at a high frequency is supplied, while the current is switched to a lower supply current for the amplifier to operate at lower frequencies.

Abstract: A digital circuit unit adaptively predicts noise and outputs the predicted noise to an analog circuit unit as a subtracter signal. The subtracter signal is input via a D/A converter to a subtractor signal wherein the noise is removed from the analog input signal. An output from the subtractor circuit is amplified by a variable gain amplifier circuit so that the amplified signal is converted into a digital signal by an A/D converter.

Abstract: A current supply circuit supplies a bias current to operational amplifiers which constitute a pipelined AD converter. A current switching circuit switches between output currents in response to a current control signal from current control means, thereby switching between currents to be supplied from a bias circuit to the operational amplifiers via transistors. A sufficiently large current enough for the amplifiers to operate at a high frequency is supplied, while the current is switched to a lower supply current for the amplifier to operate at lower frequencies.

Abstract: A cyclic AD converter having a conversion processing speed or conversion accuracy designed no higher than necessary. In the AD converter, an input analog signal is held by a sample-and-hold circuit, and converted into a digital value by an AD conversion circuit. A DA conversion circuit converts the digital value output from the AD conversion circuit into an analog value. A subtractor circuit outputs the difference between the analog value output from the AD conversion circuit and the analog value held in the sample-and-hold circuit. An amplifier circuit amplifies the output of the subtractor circuit, and feeds back the resultant to the sample-and-hold circuit and the AD conversion circuit. In the course of this feedback-based cyclic processing, an amplification control circuit changes the gain of the amplifier circuit in accordance with the progress of the circulation.

Abstract: A current supply circuit supplies a bias current to operational amplifiers which constitute a pipelined AD converter. A current switching circuit switches between output currents in response to a current control signal from current control means, thereby switching between currents to be supplied from a bias circuit to the operational amplifiers via transistors. A sufficiently large current enough for the amplifiers to operate at a high frequency is supplied, while the current is switched to a lower supply current for the amplifier to operate at lower frequencies.