This paper presents a constant-current-controlled class-C VCO using a self-adjusting replica bias circuit. The proposed class-C VCO is more suitable in real-life applications as it can maintain constant current which is more robust in phase noise performance over variation of gate bias of cross-coupled pair comparing to a traditional approach without amplitude modulation issue. The proposed VCO is implemented in 180,nm CMOS process. It achieves a tuning range of 4.8--4.9,GHz with a phase noise of -121,dBc/Hz at 1,MHz offset. The power consumption of the core oscillators is 4.8,mW and an FoM of -189,dBc/Hz is achieved.

A low distortion and low noise differential amplifier using the difference between the even- and odd-mode impedances is proposed. In order to realize an amplifier with high OIP3 and low NF characteristics, the impedance of the bias circuit should be low (<300 Ω) at the difference frequency and high (>4 kΩ) at the carrier frequency. Although the frequency response of the bias circuit impedance can only meet these conditions with difficulty, owing to the 20 MHz Tx signal bandwidth for 3G LTE, the proposed amplifier can achieve the impedance difference using the properties of a differential configuration where the difference frequency signal is the even-mode and the carrier frequency is the odd-mode. It has been demonstrated that the NF of the proposed amplifier, which has been fabricated in 0.18 µm SiGe BiCMOS technology operating at 2.14 GHz, can be kept to 1.6 dB or less and an OIP3 of 9.0 dBm can be achieved, which is 3 dB higher than that of a conventional amplifier, in the condition where the power gain is greater than 18 dB.

One of the interesting submicron MOS FET characteristics is the effect of carrier velocity saturation (CVS) on the drain current. In the CVS region, the transconductance becomes constant independent both of the gate and the drain voltage. In this paper, RF MOS amplifier design technique using the CVS region has been proposed. By setting the FET gate bias to the power supply voltage Vdd, stable operation against Vdd variations can be achieved with a simple circuit configuration. By using this, a 5 GHz amplifier has been designed and fabricated by using 0.18-µm CMOS process technology. The chip has been operated with a gain variation less than 1 dB having a peak gain of 13.5 dB from 1.2 to 2.9 V Vdd.

A novel bias circuit providing a stable quiescent current for temperature and supply voltage variations is proposed and implemented to a W-CDMA MMIC power amplifier. The power amplifier with the proposed bias circuit has the quiescent current variation of only 6% for the -30 to 90 temperature change, and 8.5% for the 2.9 V to 3.1 V supply voltage change, and the variation of the power gain at the 28 dBm output power is less than 0.8 (0.05) dB for the 0.1 V of supply voltage (60 of temperature) variation.

An L-band low quiescent current and low distortion SiGe heterojunction bipolar transistor (HBT) driver amplifier having a self base bias control circuit is described. Since the size of this bias circuit is small and it does not need an external control circuit, it is easy to be integrated with the driver amplifier on a single chip. According to the output power level, the self base bias control circuit, which is the combination of a constant base voltage circuit and p-metal oxide semiconductor (MOS) FET current mirror with a constant current source, automatically controls the base voltage, and allows low quiescent current at low output power level and low distortion at high output power level. The simulated results show that the driver amplifier having the self base bias control circuit achieves 1 dB power compression point (P1 dB) improvement of 2.4 dB compared with the driver amplifier having a conventional constant base voltage under the same quiescent current condition. The fabricated driver amplifier with the proposed bias circuit shows high P1 dB of 15.0 dBm with low quiescent current of 15.3 mA.

The temperature compensation technique of InGaP/GaAs power heterojunction bipolar transistor (HBT) with novel bias circuit using Schottky diodes has been developed. The variation in the quiescent current to the temperature is less than 30% from -30C to 90C by this technique, where that is about 125% by the conventional bias circuit. The RF performance of the power HBT MMIC with novel bias circuit shows flat temperature characteristics enough to be used for power application of wireless communications.

This paper describes a high-power and low-distortion AlGaAs/GaAs HFET amplifier developed for digital cellular base station system. We proved experimentally that distortion characteristics such as IMD (Intermodulation Distortion) or NPR (Noise Power Ratio) are drastically degraded when the absolute value of the drain bias circuit impedance at low frequency are high. Based on the experimental results, we have designed the drain bias circuit not to influence the distortion characteristics. The developed amplifier employed two pairs of pre-matched GaAs chips mounted on a single package and the total output-power was combined in push-pull configuration with a microstrip balun circuit. The push-pull amplifier demonstrated state-of-the-art performance of 140 W output-power with 11.5 dB linear gain at 2.2 GHz. In addition, it exhibited extremely low distortion performance of less than 30 dBc at two-tone total output-power of 46 dBm. These results indicate that the design of the drain bias circuit is of great importance to achieve improved IMD characteristics while maintaining high power performance.