Hitachi, Ltd.

Semiconductor Technology Academic Research Center

Nobuo Fujii

Shigetaka Takagi

Satoshi Tanaka

Kazuyuki Wada

Takahide Sato

Sigetaka Takagi

When an input signal to be amplified is very small and a large blocking signal having a high frequency is included in an input, it is necessary for a filter for mobile communication for removing thereof that a common-mode signal rejection ratio is large. Further, even in the case of an amplifier having a high gain, it is preferable that the common-mode rejection ratio is large in order to avoid saturation of the amplifier by noise. A common-mode rejecting characteristic is added to an input stage by making transconductance circuits of an input of an integrating circuit proposed by Nauta differential circuits and connecting thereof in cross connection. Thereby, a filter as well as an amplifier improving the common-mode rejection ratio of a total, are realized by being applied to a CMOS process or a BiCMOS process.

Base band filter including a semiconductor integrated circuit

A voltage-to-current conversion circuit composed of MOSFETs of the same polarity and an OTA with Rail-to-Rail with a simple configuration that uses the same have been disclosed. The voltage-to-current conversion circuit comprises a first MOSFET, to which a fixed drain-source voltage is applied all the time, and which generates a first current signal for an input voltage, a second MOSFET, which has the same polarity as that of the first MOSFET, to which the fixed drain-source voltage is applied all the time, and which generates a second current signal complementary to the first current signal for the input voltage, and a difference current operation circuit that performs the operation of subtraction between the first current signal and the second current signal, thereby an output current is generated in accordance with the input voltage.

Voltage-to-current conversion circuit and OTA using the same

When an input signal to be amplified is very small and a large blocking signal having a high frequency is included in an input, it is necessary for a filter for mobile communication for removing thereof that a common-mode signal rejection ratio is large. Further, even in the case of an amplifier having a high gain, it is preferable that the common-mode rejection ratio is large in order to avoid saturation of the amplifier by noise. A common-mode rejecting characteristic is added to an input stage by making transconductance circuits of an input of an integrating circuit proposed by Nauta differential circits and connecting thereof in cross connection. Thereby, a filter as well as an amplifier improving the common-mode rejection ratio of a total, are realized by being applied to a CMOS process or a BiCMOS process.

Semiconductor integrated circuit

A semiconductor integrated circuit comprises an amplifier circuit including a current output amplifier, a load resistor having one end connected to an output terminal of the current output amplifier and a voltage control circuit having an input terminal connected to the one end of the load resistor and an output terminal connected to an other end of the load resistor. The input terminal of the amplifier circuit serves as an input terminal of the current output amplifier, and the output terminals of the amplifier circuit serve as the individual ends of the load resistor.

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Tokyo, Japan

Nobuo Fujii