Digitally variable resistor and digital phase interpolator having the same

摘要

PURPOSE: A digital variable resistor and digital phase synthesizer thereof are provided to linearly change current by the change of a digital control code. CONSTITUTION: A digital phase synthesizer is composed of the first and the second differential amplifiers(42, 44), the first and the second digital variable resistor(46, 48) and BIOS current source(41). The first differential amplifier(42) receives the first input signal(IN1) and the reversal signal(IN1B) of the first input signal, and outputs an interpolation signal(OUT) and the reversal signal(OUTB) of the interpolation signal. The first differential amplifier(42) is equipped between a power source voltage(VDD) and the first node(N1). The second differential amplifier(44) receives the second input signal(IN2) and the reversal signal(IN2B) of the second input signal, and outputs the interpolation signal(OUT) and the reversal signal(OUTB) of the interpolation signal. the second differential amplifier(44) is equipped between power source voltage(VDD) and the second node(N2).