Fujitsu Corporation

Fugitsu Limited

Yukinori Abe

Kunihiko Gotoh

Yuji Segawa

A digitally controlled variable gain circuit which receives an analog input voltage and produces an analog output voltage. The digitally controlled variable gain circuit includes a first resistor string having first and second ends and a plurality of resistors connected in series between the first and second ends, the second end of the first resistor string being grounded and the analog input voltage being applied across the first and second ends of the first resistor string. A first selection mechanism, coupled to the first resistor string and responsive to a first digital control signal, provides a selectively determinable voltage divided output from the first resistor string. A second resistor string has first and second ends and a plurality of resistors connected in series between the first and second ends, the second end of the second resistor string being grounded and the voltage divided output provided by the first selection mechanism being applied across the first and second ends of the second resistor string. A second selection mechanism, coupled to the second resistor string and responsive to a second digital control signal, provides a selectively determinable voltage divided output from the second resistor string as the analog output voltage.

Digitally controlled variable gain circuit

A variable resistor is provided with a series resistor network including first, second and third resistor parts which are connected in series, where the second resistor part is connected to the first and third resistor parts via first and second nodes, respectively, and a fourth resistor part, coupled in parallel to the second resistor part via the first and second nodes. The fourth resistor part includes a plurality of resistors which are connected in series via a plurality of third nodes. The first resistor part has a terminal opposite the first node for receiving an input signal, and an output signal of the variable resistor is obtained via an arbitrary one of the third nodes of the fourth resistor part.

Growing community of inventors

Kawasaki, Japan

Yukinori Abe