Abstract: An circuit device includes a differential circuit including differential input terminals; a differential amplifier circuit in which differential input nodes are connected to the differential input terminals; a first power supply terminal applied a first voltage to; a second power supply terminal applied a second voltage to; a common terminal; a first resistive element of which one end is connected to one differential input terminal and another end is connected to the common terminal; a second resistive element of which one end is connected to the first supply terminal and another end is connected to the common terminal; a third resistive element of which one end is connected to one differential input terminal and another end is connected to the second supply terminal; a bonding wire, and a capacitor of which one end is connected to the second supply terminal and another end is connected to the common terminal

Abstract: A variable gain amplifier capable of stabilizing an average output potential of a differential output signal, improving power efficiency over a wide range of an amplitude of the differential input signal, and suppressing deterioration of a distortion rate is provided. The variable gain amplifier includes an amplifying circuit configured to amplify a differential input signal with a gain according to a gain control signal, and a current control circuit. The amplifying circuit has a first current source supplying a source current. The current control circuit adjusts a magnitude of the source current of the first current source according to a magnitude of the gain control signal.

Abstract: An amplifier includes a printed circuit board that includes an output terminal for outputting a electrical signal to an outside and a bias terminal for receiving a bias of the electrical signal from the outside, and an integrated circuit, a capacitor, an inductor, and a ferrite bead element mounted on the printed circuit board. The integrated circuit includes a driving circuit and an output end, and outputs the electrical signal generated by the driving circuit from the output end. The capacitor is connected between the output end and the output terminal A series circuit including the inductor and the ferrite bead element connected to each other in series, the inductor is connected to the output end, and the ferrite bead element is connected to the bias terminal.

Abstract: An amplifier including a pre-amplifier, an impedance converter, and a traveling wave amplifier (TWA) is disclosed. The pre-amplifier receives a differential input signal and has a pair of first output nodes that output a first differential signal by amplifying the differential input signal. Each first output node has first output impedance. The impedance converter includes a pair of first input nodes that receive the first differential signal and a pair of second output nodes that output a second differential signal. Each first input node has first input impedance greater than the first output impedance. The impedance converter converts the first differential signal into the second differential signal. Each second output node has second output impedance smaller than the first output impedance. The TWA includes a pair of transmission lines connected to the pair of the second output nodes. Each transmission line has characteristic impedance matching with the second output impedance.

Abstract: A traveling-wave amplifier includes a plurality of amplifier cells, an insulating layer, an input line, and an output line. The plurality of amplifier cells is provided on a semiconductor substrate. Each of the amplifier cells receives an input signal and generates a part of an output signal from the input signal. The insulating layer is provided on the semiconductor substrate. The input line is used to externally receive an input signal and to transmit the input signal to the amplifier cells respectively. The output line is used to transmit the output signal generated by the amplifier cells and to externally output the output signal. The thickness of the input line is smaller than the thickness of the output line, and the input line and the output line are provided on the same insulating layer.

Abstract: An amplifier including a pre-amplifier, an impedance converter, and a traveling wave amplifier (TWA) is disclosed. The pre-amplifier receives a differential input signal and has a pair of first output nodes that output a first differential signal by amplifying the differential input signal. Each first output node has first output impedance. The impedance converter includes a pair of first input nodes that receive the first differential signal and a pair of second output nodes that output a second differential signal. Each first input node has first input impedance greater than the first output impedance. The impedance converter converts the first differential signal into the second differential signal. Each second output node has second output impedance smaller than the first output impedance. The TWA includes a pair of transmission lines connected to the pair of the second output nodes. Each transmission line has characteristic impedance matching with the second output impedance.

Abstract: A differential amplifier includes an amplifying stage that outputs an output signal by amplifying an input signal with a gain set by a control signal, and an adjusting stage that stabilizes a DC level of the output signal. The amplifying stage includes a first source supplying a first current, and a load, and determines a ratio of a current flowing through the load to the first current depending on the input signal and the control signal, and generates the output signal from a voltage drop of the load. The adjusting stage includes a second source supplying a second current, and a monitor resistor, and generates a monitor current divided from the second current by the ratio, and duplicates the DC level as a voltage drop of the monitor resistor caused by the monitor current, and controls the first current source and the second current source depending on the DC level.

Abstract: A differential amplifier includes an amplifying stage that outputs an output signal by amplifying an input signal with a gain set by a control signal, and an adjusting stage that stabilizes a DC level of the output signal. The amplifying stage includes a first source supplying a first current, and a load, and determines a ratio of a current flowing through the load to the first current depending on the input signal and the control signal, and generates the output signal from a voltage drop of the load. The adjusting stage includes a second source supplying a second current, and a monitor resistor, and generates a monitor current divided from the second current by the ratio, and duplicates the DC level as a voltage drop of the monitor resistor caused by the monitor current, and controls the first current source and the second current source depending on the DC level.

Abstract: An amplifier circuit has: a main amplifier connected between an input terminal and an output terminal, the main amplifier amplifying an input signal input to the input terminal and outputting an amplified signal to the output terminal; a compensation circuit comprising a variable delay circuit and a variable gain inverting circuit, the variable delay circuit receiving the input signal and outputting a delay signal with a delay time from the input signal, the variable gain inverting circuit inverting and amplifying the delay signal with a gain and outputting a compensation signal to the output terminal; and a controller configured to control the gain of the variable gain inverting circuit and the delay time of the variable delay circuit to compensate a response of the main amplifier in a first frequency of a target signal of compensation and in a low frequency band higher than zero Hertz.

Abstract: A traveling-wave amplifier includes a plurality of amplifier cells, an insulating layer, an input line, and an output line. The plurality of amplifier cells is provided on a semiconductor substrate. Each of the amplifier cells receives an input signal and generates a part of an output signal from the input signal. The insulating layer is provided on the semiconductor substrate. The input line is used to externally receive an input signal and to transmit the input signal to the amplifier cells respectively. The output line is used to transmit the output signal generated by the amplifier cells and to externally output the output signal. The thickness of the input line is smaller than the thickness of the output line, and the input line and the output line are provided on the same insulating layer.

Abstract: A differential amplifier with cascade transistors connected in series to switching transistors is disclosed. The base bias of the cascade transistors is set higher than the output LOW level of the cascade transistors by a preset amount of 0.1 to 0.2V, or lower than the input HIGH level of the switching transistors by the preset amount adding to a forward voltage of a junction diode, to provide a discharge current of the base-emitter junction Cbe from the bias control, or from the upstream stage to drive the differential circuit.

Abstract: A semiconductor optical modulator includes optical input and output portions; a plurality of Mach-Zehnder modulators, each including first and second waveguide arms having first and second modulation electrodes, respectively; an optical demultiplexer coupled between the optical input portion and the Mach-Zehnder modulators through an optical waveguide; an optical multiplexer coupled between the optical output portion and the Mach-Zehnder modulators; a plurality of electrical inputs; and a plurality of differential transmission lines electrically connecting the electrical inputs to the Mach-Zehnder modulators. The first modulation electrode and the second modulation electrode of at least one of the Mach-Zehnder modulators, one of the electrical inputs, and one of the differential transmission lines that connects such one electrical input to such one Mach-Zehnder modulator form an electrical circuit having a differential impedance in a range of 80? to 95?.

Abstract: A differential circuit with a function to compensate unevenness observed in the differential gain thereof is disclosed. The differential circuit provides a low-pass filter in one of the paired transistors not receiving the input signal in addition to another low-pass filter that provides an average of output signals as a reference level of the differential circuit. The cut-off frequency of the filter is preferably set to be equal to the transition frequency at which the self-heating effect explicitly influences the trans-conductance of the transistor.

Abstract: An amplifier circuit has: a main amplifier connected between an input terminal and an output terminal, the main amplifier amplifying an input signal input to the input terminal and outputting an amplified signal to the output terminal; a compensation circuit comprising a variable delay circuit and a variable gain inverting circuit, the variable delay circuit receiving the input signal and outputting a delay signal with a delay time from the input signal, the variable gain inverting amplifier inverting and amplifying the delay signal with a gain and outputting a compensation signal to the output terminal; and a controller configured to control the gain of the pre-emphasis circuit and the delay time of the variable delay circuit to compensate a response of the main amplifier in a first frequency band lower than a base frequency of a target signal of compensation and in a low frequency band higher than zero Hertz.

Abstract: A driver circuit including front and rear amplifiers each powered by the primary and secondary power supplies, where the latter power supply is generated from the former power supply. The rear amplifier includes a cascade transistor whose base bias is provided from the bias source. The bias source provides the base bias to reduce the base current when the primary power supply is active but the secondary power supply is inactive, and to be equal to the primary power supply when two power supplies become active but the rear amplifier is inactive.

Abstract: A driver circuit including front and rear amplifiers each powered by the primary and secondary power supplies, where the latter power supply is generated from the former power supply. The rear amplifier includes a cascade transistor whose base bias is provided from the bias source. The bias source provides the base bias to reduce the base current when the primary power supply is active but the secondary power supply is inactive, and to be equal to the primary power supply when two power supplies become active but the rear amplifier is inactive.

Abstract: A semiconductor optical modulator includes optical input and output portions; a plurality of Mach-Zehnder modulators including first and second waveguide arms having first and second modulation electrodes, respectively; an optical demultiplexer coupled between the optical input portion and the Mach-Zehnder modulator through an optical waveguide; an optical multiplexer coupled between the optical output portion and the Mach-Zehnder modulator; a plurality of electrical inputs including first, second, and common electrodes disposed between the first and second electrodes; and a plurality of differential transmission lines electrically connecting the electrical inputs to the Mach-Zehnder modulators. The Mach-Zehnder modulators, the optical demultiplexer, the optical multiplexer, the electrical inputs, and the differential transmission lines are disposed on a single substrate.

Abstract: A differential amplifier with cascade transistors connected in series to switching transistors is disclosed. The base bias of the cascade transistors is set higher than the output LOW level of the cascade transistor by a preset amount of 0.1 to 0.2V, or lower than the input HIGH level of the switching transistor by the preset amount adding to a forward voltage of a junction diode, to provide a discharge current of the base-emitter junction Cbe from the bias control, or from the upstream stage to drive the differential circuit.