Patent ID: 6204789
Filing Date: 2001-03-20
Classification: H03M

Abstract:
A variable resistor circuit of digital control comprising:a first digital control variable resistor in which a combined resistance changes stepwise, said first digital control variable resistor having i resistors (i is a positive integral number which is two or greater) connected in series and a group of first digital control switches each provided between one end of the obtained combined resistor and one end of one resistor, said group of first digital control switches being on/off controlled selectively in accordance with an output signal other than an output signal corresponding to an LSB of a counter;a second digital control variable resistor connected to the first digital control variable resistor in series, said second digital control variable resistor having two resistors connected in parallel and a second digital control switch connected to one side resistor in series, said second digital control switch being on/off controlled by the output signal corresponding to the LSB of the counter; anda third digital control switch provided between both ends of the first and second digital control variable resistors connected in series, said third digital control switch being ON controlled when the counter becomes a specific value so as to short-circuit both ends of the first and second digital control variable resistors.