Fujitsu Corporation

Tomoyuki Arai

Masahiro Kudo

Shinji Yamaura

Takao Sasaki

David Enright

An amplifier circuit includes an amplifier unit and a current control circuit as means for achieving the aforementioned object. The amplifier unit includes a gain compensation MOS transistor compensating for gain of an output characteristic and a linearity compensation MOS transistor compensating for linearity of an output characteristic. A source of the gain compensation MOS transistor is connected to a drain of the linearity compensation MOS transistor. An input signal is applied to a gate of the linearity compensation MOS transistor. A drain of the gain compensation MOS transistor is set as an output. The current control circuit performs control so as to pass predetermined current between the drain and the source of the gain compensation MOS transistor and pass predetermined current between the drain and the source of the linearity compensation MOS transistor.

Amplifier circuit

An amplifying circuit includes amplifying unit comprising a first transistor unit having a gate width that is controllable and is controlled based on a first control signal.

Amplifying circuit

A bias circuit for applying a bias voltage to a nonlinear amplification circuit, including a constant-current source; and a first, second, third, and fourth transistors, wherein a current mirror circuit is configured by the first transistor and the second transistor, and the bias voltage is outputted from the drain of the second transistor, gate lengths and gate widths of the first and second transistor are the same, gate lengths of the first to fourth transistor are the same, and gate lengths and gate widths of the first, second, third, and fourth transistor are configured so that k&#x2212;kis approximately 1, where kstands for a ratio of a gate width of the third transistor to the gate width of the first transistor and kstands for a ratio of a gate width of the fourth transistor to the gate width of the first transistor.

Bias circuit and control method for bias circuit

A converting circuit for converting differential signals to a single-ended signal. The converting circuit comprises a cascode amplifier comprising a first transistor and a second transistor, wherein the first transistor comprises a control terminal, a first terminal, and a second terminal, the control terminal to which one of the differential signals is input, the control terminal being electrically-grounded; and, the second transistor comprises a first terminal and a second terminal, the first terminal of the second transistor being connected to the first terminal, the second terminal of the second transistor from which output signal is outputted, a capacitor for adjusting the phase, the capacitor being connected to the second terminal; and a current source being connected to the second terminal.

Converting circuit for converting differential signal to single-ended signal

A conversion circuit for converting a differential signal into a single-phase signalhas a source-follower amplifierand a source-grounded amplifier. The source-follower amplifieroutputs a non-inverted signal IN of the differential signal the phase of which is not inverted. The source-grounded amplifierinverts an inverted signal INX of the differential signal and adjusts its phase to that of the non-inverted signal IN. At point A, differential signals IN, INX are added and output as a single-phase signal OUT.

Conversion circuit for converting differential signal into signal-phase signal

A power control circuit includes: a fine adjustment variable amplifying unit configured to amplify the input signal in accordance with a first gain set value; a coarse adjustment variable amplifying unit configured to amplify the input signal in accordance with a second gain set value; a branching unit configured to branch an output signal into a feedback signal; a comparing unit configured to compare a gain value between the input signal and the output signal with the required gain set value; a control unit configured to determine the first gain set value and the second gain set value based on the required gain set value; and an adjusting unit configured to adjust the first gain set value and the second gain set value so that the power value of the feedback signal becomes a power value corresponding to the required gain set value.

Power control circuit and power control method

A gm compensation current source controls current that runs through a current source transistor, source-grounded transistors that determine a gain so that mutual conductance gm of the source-grounded transistors is compensated and the gain is compensated. A 1/r current source runs current inversely proportional to variation of load resistors of an amplifier so that gate bias points of gate-grounded transistors that are connected to the source-grounded transistors remain constant, and deterioration of linearity at a drain terminal of a gate-grounded transistor is suppressed.

Bias circuit

A variable gain amplifier has a first amplifier circuit () having a first field-effect transistor and amplifying a signal input to a gate of the first field-effect transistor to output; a gate bias control circuit () controlling a gate bias of the first amplifier circuit to control a gain of the first amplifier circuit; and a variable matching circuit () controlling a capacitor connected to the gate of the first amplifier circuit to control the gain of the first amplifier circuit.

Variable gain amplifier and control method thereof

The present invention is an amplifier circuit that permits variable gain control, comprising an input terminal to which a high frequency input signal is supplied; an amplifier transistor to the gate of which the high frequency input signal supplied to the input terminal is supplied and which generates an amplified signal at the drain side; and a variable attenuator provided in a signal transmission line between the input terminal and the gate of the amplifier transistor, in which a plurality of attenuation units in which an attenuation capacitor and a switch transistor are serially connected are provided in parallel between the signal transmission line and a power supply, and the attenuation ratio of which is variably controlled by controlling the conduction of the switch transistor.

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Kawasaki, Japan

Tomoyuki Arai