Fujitsu Corporation

Other

Kouji Okada

Teruhiko Saitou

Shinji Miyata

Yukisato Miyazaki

Masao Iijima

Hiroyuki Matsunami

A control signal that runs a control oscillator of a signal generation circuit that generates a write clock is taken as a reference signal. That reference signal is supplied to a signal generation circuit that generates a read clock. In the signal generation circuit that generates the read clock, there is no need to generate a reference signal within its own circuits, which makes it possible to supply it to a control oscillator by adding the error timing from reading out the signal against the supplied reference signal. In this way, no means for locking the read clock into the initial frequency is needed and neither is the time for locking the read clock to the initial frequency (lock up time). This makes it possible to reduce the size of the circuit and to reduce the signal read-out time.

Signal generating circuit, timing recovery PLL, signal generating system and signal generating method

A spread spectrum clock generation circuit capable of further reducing the electromagnetic wave radiation with a simple configuration has been disclosed and, particularly in a spread spectrum clock generation circuit using a current control oscillator (ICO), a differential signal to which a spread spectrum modulation signal, the period or amplitude of which changes, is added is generated, and the differential signal is applied to the ICO and a clock is generated.

Spread spectrum clock generation circuit, jitter generation circuit and semiconductor device

A trans-conductance filter circuit with an expanded cut-off frequency range is provided. The cut-off frequency of a trans-conductance filter circuit is changed by varying the current mirror ratio of a current mirror circuit. This mirror ratio is varied by changing the output current of a constant current source, or by switching among the respective action states of multiple transistors the actions of which are invoked within constant current regions. The variable cut-off frequency range can be expanded without losing the constant current attributes of the transistors.

Trans-conductance amplification circuit, trans-conductance filter circuit, and filtering method

The present invention provides an A/D converter. An upper comparison voltage generator divides a reference voltage into a plurality of large-level regions with series-connected first voltage-dividing elements, and outputs voltages at boundaries of the individual large-level regions as upper comparison voltages. Upper comparators compare an analog input voltage with the individual upper comparison voltages. An upper encoder determines, from output signals of the upper comparators, to which one of the large-level regions the analog input voltage belongs, and outputs a predetermined upper digital code corresponding to the determined large-level region. A lower comparison voltage generator divides the large-level region to which the analog input voltage is determined to belong by the upper encoder, into a plurality of small-level regions with second voltage-dividing elements and outputs voltages at boundaries of the individual small-level regions as lower comparison voltages. Lower comparators compare the analog input voltage with the individual lower comparison voltages. A lower encoder determines, from output signals of the lower comparators, to which one of the small-level regions the analog input voltage belongs, and outputs a predetermined lower digital code corresponding to the determined small-level region.

Three-step converter

An operational amplifier having a high voltage power supply and a low voltage power supply receives first and second input signals and amplifies a voltage difference between the first and second input signals to generate an amplified signal. The operational amplifier has a first differential amplifier having a pair of first type transistors that are activated by the first and second input signals having a voltage greater than the voltage of the low voltage power supply. The first differential amplifier transmits a first output signal (S1) in response to the voltage difference between the first and second input signals. A second differential amplifier has a pair of second type transistors that are activated by the first and second input signals having a voltage smaller than the voltage of the high voltage power supply. The second differential amplifier transmits a second output signal (S2) in response to the voltage difference between the first and the second input signals. An output circuit synthesizes the first and second output signals. The output circuit is activated by a synthesized signal to transmit the amplified signal.

Operational amplifier having rail to rail input/output ability

An improved method and apparatus related to a comparator particularly suited for use in an A/D converter so as to obtain a high resolution, which results in a reduced circuit area and operates with low power consumption. To compare an analog input voltage and reference voltages, the comparator includes chopper type comparators for producing comparison voltages and determination signals, and includes a determination circuit for producing one or more additional determination signals. The chopper type comparators may further include amplifiers and determination circuits.

Growing community of inventors

Kasugai, Japan

Kouji Okada