Current type ring oscillator, and voltage-controlled oscillator having current type ring oscillator

摘要

A current type inverter circuit used in a Current Type Ring Oscillator and a Voltage-Controlled oscillator operates at a high speed with a low power consumption. A reference power source 1 has one end connected to a power source VDD and the other source receiving a reference current Iref. A drain and a gate of an NMOS transistor Q1 of a current mirror circuit CM1, as an input part, receive an input current Iin. A drain of an NMOS transistor Q2 is connected to an node N1 of the other end side of the reference power source 1 as an output part. As an input part, a drain and a gate of an NMOS transistor Q3 of a current mirror circuit CM2 are connected to the node N1 while a drain of an NMOS transistor Q4 functions as an output part for outputting an output current Iout. The transistors are set so that all of the conditions TS1>/=1, TS2>/=1 and TS1xTS2>1 are satisfied where TS1 is a ratio of the size of the NMOS transistor Q2 to the size of the NMOS transistor Q1 and TS2 is a ratio of the size of the NMOS transistor Q4 to the size of the NMOS transistor Q3.