Armstrong, Westerman & Hattori, LLP
Variable resistance circuit, operational amplification circuit, semiconductor integrated circuit, time constant switching circuit and waveform shaping circuit
Eight resistors having resistance values of R&times;2i (i=0 to 7) (&OHgr;) are serially connected while eight switches exhibiting parasitic resistance values of r&times;2i (&OHgr;) in ON states are connected in parallel with the resistors respectively, for changing a resistance value by turning on/off the switches. The resistors are connected between an inversion input terminal of an operational amplifier and a terminal, and a non-inversion input terminal receives a prescribed reference voltage. Between the inversion input terminal and an output terminal of the operational amplifier, a resistor and a switch of a variable resistance circuit forming a negative feedback loop are connected to the output terminal while another resistor and another switch are connected to the inversion input terminal. In the variable resistance circuit, the resistance values of the resistors are successively increased from the side of the terminal, so that the resistor connected to the inversion input terminal has the maximum resistance value. Thus, only a single node is present ahead of the last resistor while a parasitic capacitance is minimized, whereby the frequency characteristic of an operational amplification circuit can be improved.
Sanyo Electric Co., Ltd.
G H
G06G H03G
inventional inventional
Takeshi Atsushi Kuniyuki
Otsuka Wada Tani