Low-noise, fast-response low-drop-out regulators for RF applications

As CMOS technology is rapidly moving to deep submicron gate lengths, supply voltages for analog and RF circuitry are continuously decreasing. This introduces new challenges for the design of RF and analog circuits. One of the main challenges is the drastic reduction on the supply voltage which limits the linearity, dynamic range, and increases the supply ripple sensitivity of the circuits. With the reduction of the RF IC's supply voltage, noise, ripple and cross-coupling on the power supply starts playing a dominant role in the transceiver noise budget. To overcome noise budget in analog and RF circuitry, well-designed voltage regulators are required. This regulator should have low noise and fast transient characteristics for improving analog and RF circuits' performance and also requires good current efficiency for battery life.; The proposed research consists of designing, modeling, and characterizing three types of low-dropout (LDO) regulator architectures. The focus is on low-power portable applications such as mobile phones, PDAs and laptops, where small area, low cost, low noise, high power supply rejection and high efficiency are the primary design objectives. The first proposed LDO regulator utilizes a current feedback buffer amplifier to achieve fast transient response. The other two LDO regulators focus on low noise characteristics for RF applications. The second proposed LDO regulator is a low 1/f noise LDO regulator which employs chopper stabilization techniques. Using a chopper stabilization technique, noise at low frequencies of the error amplifier, which is one of the dominant noise sources, especially 1/f noise, is surprisingly reduced. This technique is also used to reduce output noise of the reference circuit, which is another dominant noise source in LDO regulators. To improve power supply rejection (PSR), a supply rejection subtraction stage has been included. The third proposed LDO regulator utilizes chopper stabilization techniques to reduce 1/f noise at low frequencies, a current feedback amplifier to improve transient response, and a delta-sigma (DeltaSigma) noise shaper to reduce the tonal energy at the chopping frequency due to clock feedthrough via chopper switches. Three types of LDO regulators could be utilized as a power management circuitry in RF applications.