Abstract: An amplifier applied to TIA is provided to suppress the noise caused by a current source. An amplifier constituting a transimpedance amplifier includes an inductor element inserted between a current source connected to an input terminal of an amplification stage and a power source voltage line. The current source includes a first transistor in which a base terminal is connected to a current control bias and a collector terminal is connected to the input terminal. The inductor element is inserted between the emitter terminal of the first transistor and the power source voltage line.

Abstract: An amplifier typically exemplified by a TIA is realized that provides an optimal band characteristic, that reduces the possibility of the oscillation, and that achieves a reduced dispersion of the band characteristics. An amplifier for amplifying an electric signal, comprising: a first buffer for amplifying the electric signal; a filter that is connected to an output of the first buffer and that includes a parallel circuit consisting of an inductor and a first capacity; and a second buffer connected to an output of the filter.

Abstract: A positive-side power supply terminal (1-1a) of a differential amplifier (1-1) is connected to a positive-side power supply line (L1). A negative-side power supply terminal (1-2b) of a differential amplifier (1-2) is connected to a negative-side power supply line (L2). A negative-side power supply terminal (1-1b) of the differential amplifier (1-1) and a positive-side power supply terminal (1-2a) of the differential amplifier (1-2) are connected to each other. A final-stage amplifier (2) is connected between the positive-side power supply line (L1) and the negative-side power supply line (L2).

Abstract: A driver circuit 11 includes a plurality of cascode-connected NMOS transistors, a modulating signal VGN1 is applied to a gate terminal of a lowermost stage transistor TN1 located at a lowermost stage out of the NMOS transistors, and an upper stage bias potential VGN2 that is a sum of a minimum gate-source voltage VGN1min and a maximum drain-source voltage VDS1max of a transistor (TN1) located immediately below an upper stage transistor located at an upper stage above the lowermost stage transistor of the NMOS transistors is applied to the upper stage transistor TN2.

Abstract: An amplifier applied to TIA is provided to suppress the noise caused by a current source. An amplifier constituting a transimpedance amplifier includes an inductor element inserted between a current source connected to an input terminal of an amplification stage and a power source voltage line. The current source includes a first transistor in which a base terminal is connected to a current control bias and a collector terminal is connected to the input terminal. The inductor element is inserted between the emitter terminal of the first transistor and the power source voltage line.

Abstract: An amplifier typically exemplified by a TIA is realized that provides an optimal band characteristic, that reduces the possibility of the oscillation, and that achieves a reduced dispersion of the band characteristics. An amplifier for amplifying an electric signal, comprising: a first buffer for amplifying the electric signal; a filter that is connected to an output of the first buffer and that includes a parallel circuit consisting of an inductor and a first capacity; and a second buffer connected to an output of the filter.

Abstract: A driver circuit 11 includes a plurality of cascode-connected NMOS transistors, a modulating signal VGN1 is applied to a gate terminal of a lowermost stage transistor TN1 located at a lowermost stage out of the NMOS transistors, and an upper stage bias potential VGN2 that is a sum of a minimum gate-source voltage VGN1min and a maximum drain-source voltage VDS1max of a transistor (TN1) located immediately below an upper stage transistor located at an upper stage above the lowermost stage transistor of the NMOS transistors is applied to the upper stage transistor TN2.

Abstract: An optical modulator driver circuit (1) includes an amplifier (50, Q10, Q11, R10-R13), and a current amount adjustment circuit (51) capable of adjusting a current amount of the amplifier (50) in accordance with a desired operation mode. The current amount adjustment circuit (51) includes at least two current sources (IS10) that are individually ON/OFF-controllable in accordance with a binary control signal representing the desired operation mode.

Abstract: A positive-side power supply terminal (1-1a) of a differential amplifier (1-1) is connected to a positive-side power supply line (L1). A negative-side power supply terminal (1-2b) of a differential amplifier (1-2) is connected to a negative-side power supply line (L2). A negative-side power supply terminal (1-1b) of the differential amplifier (1-1) and a positive-side power supply terminal (1-2a) of the differential amplifier (1-2) are connected to each other. A final-stage amplifier (2) is connected between the positive-side power supply line (L1) and the negative-side power supply line (L2).

Abstract: A transimpedance amplifier circuit (1) includes an amplifier (22) that amplifies a received signal, an automatic gain control (AGC) circuit (2) that controls the amplification gain of the amplifier by a first time constant in accordance with the level of the received signal, and a first selection circuit (25) that selects the first time constant from a plurality of predetermined values. This can simultaneously implement a short time constant of an AGC function necessary to instantaneously respond to a burst signal and a long time constant of the AGC function necessary to obtain a satisfactory bit error rate (BER) characteristic in a continuous signal by an inexpensive and compact circuit arrangement.

Abstract: A transimpedance amplifier circuit (1) includes an amplifier (22) that amplifies a received signal, an automatic gain control (AGC) circuit (2) that controls the amplification gain of the amplifier by a first time constant in accordance with the level of the received signal, and a first selection circuit (25) that selects the first time constant from a plurality of predetermined values. This can simultaneously implement a short time constant of an AGC function necessary to instantaneously respond to a burst signal and a long time constant of the AGC function necessary to obtain a satisfactory bit error rate (BER) characteristic in a continuous signal by an inexpensive and compact circuit arrangement.

Abstract: An optical modulator driver circuit (1) includes an amplifier (50, Q10, Q11, R10-R13), and a current amount adjustment circuit (51) capable of adjusting a current amount of the amplifier (50) in accordance with a desired operation mode. The current amount adjustment circuit (51) includes at least two current sources (IS10) that are individually ON/OFF-controllable in accordance with a binary control signal representing the desired operation mode.

Abstract: An optical signal detection circuit (10) includes an amplification circuit (11) that differentially amplifies an electrical signal (Tout) corresponding to the pulse train of an optical signal (Pin) and outputs a differential output signal (Aout), and a comparator (12) that compares the voltage value of the positive-phase signal of the differential output signal (Aout) with the voltage value of the negative-phase signal and outputs a pulsed comparison output signal (Cout) corresponding to the comparison result. The amplification circuit (11) includes a current addition circuit (11E) that adjusts a DC load current to generate a positive-phase signal (Aout+) and a negative-phase signal (Aout?) of the differential output signal (Aout) in accordance with an adjusted voltage value from an external adjusted voltage source (Vadj) and adjusts the DC bias of the positive-phase signal (Aout+) and the DC bias of the negative-phase signal (Aout?).

Abstract: A comparator (11) outputs, out of an electrical signal input from a trans impedance amplifier (TIA) via a coupling capacitor, pulses having amplitudes equal to or larger than a reference value as a comparison output signal (Cout). An analog holding circuit (12) charges a holding capacitor with each pulse contained in the comparison output signal (Cout) and also removes a DC voltage obtained by the charging via a discharging resistor, thereby generating a holding output signal (Hout) that changes in accordance with the presence/absence of input of an optical signal. This allows to perform an autonomous operation without any necessity of an external control signal and properly detect the presence/absence of input of an optical signal.

Abstract: An optical signal detection circuit (10) includes an amplification circuit (11) that differentially amplifies an electrical signal (Tout) corresponding to the pulse train of an optical signal (Pin) and outputs a differential output signal (Aout), and a comparator (12) that compares the voltage value of the positive-phase signal of the differential output signal (Aout) with the voltage value of the negative-phase signal and outputs a pulsed comparison output signal (Cout) corresponding to the comparison result. The amplification circuit (11) includes a current addition circuit (11E) that adjusts a DC load current to generate a positive-phase signal (Aout+) and a negative-phase signal (Aout?) of the differential output signal (Aout) in accordance with an adjusted voltage value from an external adjusted voltage source (Vadj) and adjusts the DC bias of the positive-phase signal (Aout+) and the DC bias of the negative-phase signal (Aout?).

Abstract: A comparator (11) outputs, out of an electrical signal input from a trans impedance amplifier (TIA) via a coupling capacitor, pulses having amplitudes equal to or larger than a reference value as a comparison output signal (Cout). An analog holding circuit (12) charges a holding capacitor with each pulse contained in the comparison output signal (Cout) and also removes a DC voltage obtained by the charging via a discharging resistor, thereby generating a holding output signal (Hout) that changes in accordance with the presence/absence of input of an optical signal. This allows to perform an autonomous operation without any necessity of an external control signal and properly detect the presence/absence of input of an optical signal.

Abstract: Providing a CDR circuit having a stable clock extracting function and a data regenerating function with a high-speed data input process by reducing the operation speed of the phase comparator circuit. With a phase comparator circuit capable of operating with a clock signal whose period is 2 times the unit time width of the inputted data signal, the pulse width of the phase error signal, representing the difference in phase between the transition point of the data signal and the transition point of the clock signal, is extended as much as the unit time width of the data signal.

Abstract: Providing a CDR circuit having a stable clock extracting function and a data regenerating function with a high-speed data input process by reducing the operation speed of the phase comparator circuit. With a phase comparator circuit capable of operating with a clock signal whose period is 2 times the unit time width of the inputted data signal, the pulse width of the phase error signal, representing the difference in phase between the transition point of the data signal and the transition point of the clock signal, is extended as much as the unit time width of the data signal.

Abstract: A pulse tube refrigerator which reduces valve losses in a cycle and improves refrigeration efficiency includes a pressure oscillator, a refrigerating portion, a first middle pressure buffer tank, a first middle pressure buffer side valve, a second middle pressure buffer tank and a second middle pressure buffer side valve. A regenerator in the refrigerating portion and an outlet port and an inlet port of a compressor in the pressure oscillator are connected via a high pressure valve and a low pressure valve respectively. A high temperature heat exchanger of the refrigerating portion and the first middle pressure buffer tank and the second middle pressure buffer tank are connected via the first middle pressure buffer side valve and the second middle pressure buffer side valve. The first middle pressure buffer tank and the second middle pressure buffer tank include different middle pressures which are predetermined between an output pressure and an input pressure of the compressor.

Abstract: A pulse tube refrigerator includes a compressor, a first heat exchanger, a first regenerator, a first cold head, a first pulse tube, a first radiator, a second regenerator, a second cold head, a second pulse tube, a second radiator, an orifice and a buffer tank which are connected in series. A first cooling part consists of the first heat exchanger, the first regenerator, the first cold head, the first pulse tube and the first radiator. A second cooling part consists of the first radiator, the second regenerator, the second cold head, the second pulse tube and the second radiator. The first radiator forms not only the radiator of the first cooling part, but also the heat exchanger of the second cooling part.