Low Phase Noise Differential LC tank VCO with Current Negative Feedback

摘要

A low phase noise differential LC tank VCO(Voltage Controlled Oscillator) having a current negative feedback circuit is provided to constrain the noises of a lower frequency and a high frequency generated from a couple of cross connections and a tail current source by installing a current negative feedback circuit on a differential emitter-degeneration VCO. A low phase noise differential LC tank VCO with a current negative feedback circuit includes an LC tank resonant unit(200), first and second oscillation transistors(211,212), first and second emitter driving units(320-1,320-2), and first and second negative feedback transistors(341,342). The LC tank resonant unit provides an inductance and a capacitance between a power voltage terminal and a first connection terminal, and between the power voltage terminal and a second connection terminal. The first and second oscillation transistors are connected to the first connection terminal and the second connection terminal, and form a collector-base cross connection. The first and second emitter driving units(320-1,320-2) are operated as a current source for driving each oscillation transistor(211,212). The first and second negative feedback transistors(341,342) receive an emitter output of each of the oscillation transistors, offsets influence of a noise which is applied and amplified in a base of the oscillation transistors.