Patent ID: 6081166
Filing Date: 2000-06-27
Classification: H03K,H03L

Abstract:
A voltage controlled oscillator formed as a ring oscillator, comprising:n (n.gtoreq.3) number of logical buffer circuits connected in series from a first logical buffer circuit to an n-th logical buffer circuit, each logical buffer circuit having a differential input terminal and a differential output terminal, wherein an i-th (1.ltoreq.i<n) differential output terminal is connected to an i-th+1 differential input terminal, and wherein the differential output terminal of the n-th logical buffer circuit is made a negative feedback to the differential input terminal of said first logical buffer circuit, each said logical buffer circuit comprising:a differential transistor pair including a first transistor and a second transistor, each differential transistor having an emitter terminal, a collector terminal, and a base terminal, wherein said base terminals comprise a differential input;a first diode array including m (m>1) number of diodes connected in series, said first diode array being connected to said collector terminal of said first transistor;a second diode array including m number of diodes connected in series, said second diode array being connected to said collector terminal of said second transistor;a first capacitor, said first capacitor having a terminal connected to said collector terminal of said first transistor;a second capacitor, said second capacitor having a terminal connected to said collector terminal of said second transistor;a frequency control current source, said frequency control current source setting a sum of current flowing through said emitter terminals of said first and second transistors;a first current source connected in parallel with said first diode array, said first current source supplying a current which is proportional to, and has a value not more than one-half of, said frequency control current source; anda second current source connected in parallel with said second diode array, said second current source supplying a current which is proportional to, and has a value not more than one-half of, said frequency control current source.