Abstract: The frequency synthesizer circuit includes a phase-locked loop (PLL) circuit, a voltage controlled oscillator (VCO), a low pass filter (LPF), an input terminal for providing serial data provided from the exterior to the PLL circuit, an output terminal for providing an oscillation signal provided the VCO, and a testing unit providing a testing voltage with a binary value to the VCO, wherein, the PLL circuit, the VCO, the LPF, and the testing unit are mounted on a single chip, and usability of the frequency synthesizer circuit is determined based on the oscillation signal provided from the VCO via said output terminal according to the testing voltage with a binary value provided from said testing unit.

Abstract: An adjustment unit in a self-adjustment device searches for an output frequency band that conforms to a reference frequency of a given signal provided from the exterior by comparing the reference frequency and the output frequency band corresponding to a first medium of a plurality of output frequency bands provided from a voltage controlled oscillator (VCO) in a PLL circuit. Depending on whether the reference frequency is higher or lower than the output frequency band corresponding to the first medium of the plurality of output frequency bands, the adjustment unit further compares the reference frequency and the output frequency band corresponding to a second medium of either a half having high output frequency bands or a half having low output frequency bands of the plurality of output frequency bands, which halves are divided having the output frequency band corresponding to the first medium as a center.

Abstract: The frequency synthesizer circuit includes a phase-locked loop (PLL) circuit, a voltage controlled oscillator (VCO), a low pass filter (LPF), an input terminal for providing serial data provided from the exterior to the PLL circuit, an output terminal for providing an oscillation signal provided the VCO, and a testing unit providing a testing voltage with a binary value to the VCO, wherein, the PLL circuit, the VCO, the LPF, and the testing unit are mounted on a single chip, and usability of the frequency synthesizer circuit is determined based on the oscillation signal provided from the VCO via said output terminal according to the testing voltage with a binary value provided from said testing unit.

Abstract: A voltage controlled oscillator (VCO) having an amplifier including a field-effect transistor (FET). The VCO includes a voltage controlled capacitor having an inversion amplifier including an FET, an amp gain of the inversion amplifier being controlled by a voltage; and a capacitor connected between an input and an output of the inversion amplifier.