Yokogawa Electric Corporation

Daisuke Hatori

Takashi Yoshida

Yusaku Yoshida

Youichi Iwano

Tadahiko Takayama

A current-to-voltage conversion circuit according to one aspect of the present invention includes a first resistor, a first current source, a first capacitor, a first output terminal, a first voltage source, a first transistor, and a second resistor. The first resistor includes a first end and a second end. The first end of the first resistor is connectable to an electrode included in a sensor and the second end of the first resistor is connected to a first electrical potential. The first capacitor includes a first end and a second end. The first end of the first capacitor is connected to the first end of the first resistor and the second end of the first capacitor is connected to the first current source. The first transistor includes a first terminal, a second terminal, and a control terminal. The first terminal is connected to the second end of the first capacitor, the second terminal is connected to the first output terminal, and the control terminal is connected to the first voltage source. The second resistor includes a first end connected to the second terminal and a second end connected to a second electrical potential.

Current-to-voltage conversion circuit and self-oscillation circuit

A current output circuit for a two-wire transmitter includes a first current source circuit configured to output a first current controlled by a control voltage generated based on a physical quantity, a second current source circuit configured to output a second current controlled by the first current, a first shunt voltage source circuit configured to generate an internal power source of the two-wire transmitter from the second current, a third current source circuit configured to generate a third current controlled by a reference voltage, and a second shunt voltage source circuit configured to generate a power source of the second current source circuit by the third current. The current output circuit is configured to output a predetermined current controlled by the control voltage based on the first current, the second current and the third current to an external circuit through two transmission lines.

Current output circuit and two-wire transmitter

A two-wire transmitter starter circuit is configured to stably supply power at the time of start-up. The two-wire transmitter starter circuit includes a starter current generation circuit. The starter current generation circuit is connected in parallel with a current conversion unit configured to convert a detection signal of a sensor to a predetermined DC current. The starter current generation circuit includes a first series circuit where a first resistor and a shunt regulator are connected in series, and a second series circuit where a switching element and a second resistor are connected in series. The shunt regulator includes a first control terminal connected to a connection point of the switching element and the second resistor. The switching element includes a second control terminal connected to a connection point of the first resistor and the shunt regulator.

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Musashino, Japan

Daisuke Hatori