Abstract: Provided is a voltage controlled oscillator to which a switching bias technique is applied so as to lower flicker noise of a bias circuit and enhance phase noise characteristics, thereby reducing the overall chip area to make it possible to achieve integration. A common mode voltage applied to the bias circuit is negatively fed back to an oscillation waveform. Therefore, it is possible to stabilize the magnitude of the oscillation waveform of the voltage controlled oscillator with respect to a change in an external condition.

Abstract: Provided is a wideband active balun circuit based on a differential amplifier. The active balun circuit is configured to compensate for unbalance between two differential signals and can be applied to wideband systems, such as software defined radio (SDR) systems or ultra wideband (UWB) systems. Also, when signal unbalance is caused by changes in process conditions, such as temperature, errors in amplitude and phase between the two differential signals can be finely tuned by adjusting a voltage tuning terminal outside a chip, so that the active balun circuit can simply solve the unbalance between the two differential signals. Furthermore, input transistors that constitute a pair of differential amplifiers are provided in a cascode structure to prevent the occurrence of signal leakage and self-mixture.

Abstract: Provided is a differential varactor using a gated varactor, which has a wider tuning range and a better linearity and minimum to maximum capacitance ratio than conventional PN-junction and MOS varactors. Thus, the differential varactor having a wider tuning range, and better linearity and common-mode rejection ratio may be implemented.

Abstract: Provided is a voltage controlled oscillator to which a switching bias technique is applied so as to lower flicker noise of a bias circuit and enhance phase noise characteristics, thereby reducing the overall chip area to make it possible to achieve integration. A common mode voltage applied to the bias circuit is negatively fed back to an oscillation waveform. Therefore, it is possible to stabilize the magnitude of the oscillation waveform of the voltage controlled oscillator with respect to a change in an external condition.

Abstract: Provided is a wideband active balun circuit based on a differential amplifier. The active balun circuit is configured to compensate for unbalance between two differential signals and can be applied to wideband systems, such as software defined radio (SDR) systems or ultra wideband (UWB) systems. Also, when signal unbalance is caused by changes in process conditions, such as temperature, errors in amplitude and phase between the two differential signals can be finely tuned by adjusting a voltage tuning terminal outside a chip, so that the active balun circuit can simply solve the unbalance between the two differential signals. Furthermore, input transistors that constitute a pair of differential amplifiers are provided in a cascode structure to prevent the occurrence of signal leakage and self-mixture.