Fujitsu Corporation

Hideki Oku

Yukito Tsunoda

Satoshi Ide

An amplification circuit coupled to another circuit by alternating current (AC) coupling includes: an amplifier that amplifies and outputs a signal input from the other circuit or amplifies an input signal and outputs the amplified input signal to the other circuit; a feedback circuit that positively feeds back the signal output from the amplifier to an input of the amplifier; and a low pass filter that attenuates a high frequency component of the signal positively fed back to the input of the amplifier by the feedback circuit, and in which a higher cut-off frequency is set such that a lower cut-off frequency in a combination of the amplification circuit and a high pass filter formed by the AC coupling is lower than a lower cut-off frequency in the high pass filter.

Amplification circuit, optical module, and amplification method

An amplifier circuit includes: a first transistor and a second transistor of which collectors/drains are coupled to a first power-source via a first load-impedance-element and the first power-source via a second load-impedance-element, respectively; a gain-adjustment-resistance-element that is connected to an emitter/source of the first transistor and an emitter/source of the second transistor; a first current-source and a second current-source that are connected to the emitters/the sources of the first transistor and the second transistor respectively, and a second power-source; a third transistor and a fourth transistor of which collectors/drains are connected to the first power-source and bases/gates are connected to the first load-impedance-element and the second load-impedance-element, respectively; a first feedback-resistance-element that is connected to a base/gate of the first transistor and an emitter/source of the third transistor; and a second feedback-resistance-element that is connected to a base/gate of the second transistor and an emitter/source of the fourth transistor.

Amplifier with gain adjustment resistor, feedback resistors and transistors and optical receiver including amplifier

A receiver circuit includes a first amplifier circuit to differentially amplify differential input signals by a linear operation, a second amplifier circuit configured to differentially amplify output differential signals of the first amplifier circuit by a limiting operation, a feedback circuit, first and second resistors coupled between the feedback circuit and outputs of the first amplifier circuit, and third and fourth resistors coupled between the feedback circuit and outputs of the second amplifier circuit. The feedback circuit amplifies a positive-phase signal that is output from a positive-phase output node thereof coupled to the first and third resistors, and a negative-phase signal that is output from a negative-phase output node thereof coupled to the second and fourth resistors, and feeds back a feedback signal after amplification to the first amplifier circuit.

Receiver circuit

An amplifierincluding a first transistorwhich is a common base transistor and whose emitter current fluctuates in accordance with fluctuations in an input current that is input to the emitter, a second transistorwhich is a common base transistor, whose emitter is connected to the collector of the first transistor, and whose collector voltage fluctuates in accordance with fluctuations in the emitter current of the first transistor, a third transistorwhich is a common collector transistor and whose base is connected to the collector of the second transistor, and an amplification unitto which an emitter voltage of the third transistoris input and which outputs an amplified voltage obtained by amplifying the emitter voltage of the third transistor, wherein the base resistance of the second transistoris higher than the base resistance of the first transistor

Amplifier

A signal reproduction circuit, includes: a clock reproduction circuit configured to reproduce a reception clock from a reception data signal; a data fetching circuit configured to fetch the reception data signal in response to a variation edge of the reception clock and output the reception data signal as first decision data; and a phase adjustment circuit configured to adjust a phase of the variation edge of the reception clock in response to a plurality of second decision data, the data fetching circuit fetching a plurality of second reception data in a plurality of periods immediately preceding to a period in which the reception data signal is fetched and outputting the plurality of second reception data as the plurality of second decision data.

Signal reproduction circuit, signal reproduction system, and signal reproduction method

An amplifier circuit includes: an input pad to receive a current signal; a conversion section to convert the current signal into a voltage signal; an inductor electrically connected in series between the input pad and the conversion section; and a storage element, one end of the storage element electrically coupled between the inductor and the conversion section, the other end of the storage element electrically coupled to a ground.

Amplifier circuit and light receiving circuit

A signal shaping circuit that shapes a drive signal and includes a main-signal amplifying circuit that amplifies the drive signal; a preemphasis generating circuit that symmetrically emphasizes a rising portion and a falling portion of the drive signal; a current source that is provided in the main-signal amplifying circuit; and a condenser that couples the main-signal amplifying circuit and the preemphasis generating circuit.

Signal shaping circuit

There is provided a digital-to-analog converter including: a mirror circuit including a first transistor to copy a reference current at a predetermined mirror ratio, and a second transistor cascade coupled with the first transistor; and an analog switch coupled with a gate of the second transistor, the analog switch being configured to be controlled, by a digital signal input from outside, so as to be turned on or off.

Digital-to-analog converter

A driver circuit includes a plurality of delay circuits and an inverter. The plurality of delay circuits delay branched driving signals. The inverter inverts at least one of the branched driving signals. At least one of the plurality of delay circuits is at least one variable delay circuit delaying a variable amount of delay. The output driving signal is output by combining the inverted signal of the branched driving signal output via at least one inverter and at least one non-inverted signal of the branched driving signals output from the delay circuits.

Driver and optical transmission apparatus

A driving circuit includes a first delay circuit, a rise-detection circuit, a fall-detection circuit, a first filter, a second filter, and an adder. The first delay circuit delays an input signal. The rise-detection circuit detects a rise of the input signal. The fall-detection circuit detects a fall of the input signal. The first filter gives a first gain-frequency response to an output signal of the rise-detection circuit. The second filter gives a second gain-frequency response to an output signal of the fall-detection circuit. The adder adds an output signal of the first filter and an output signal of the second filter to an output signal of the first delay circuit.

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Isehara, Japan

Hideki Oku