Comparative Analysis of Simulation-Based Methods for Deriving the Phase- and Gain-Margins of Feedback Circuits With Op-Amps

This article proposes an LDO with fast response to load transients that can handle any practical capacitive loads. These features are mainly due to a novel frequency compensation circuit tailored for its error amplifier, which is based on an improved version of the popular common gate amplifier. A simple yet effective approach to the small-signal analysis of LDO with multiple feedback loops is employed to analyse intuitively the LDO and derive key design constraints. Simulation and measurement results performed on a test chip implemented in standard 130nm CMOS process validated the proposed LDO. It requires only 0.7µA quiescent current but exhibits an excellent response to load transients: when the load current jumps from 0A to 100mA in 1µs the output voltage presents an undershoot of 76mV and an overshoot of 198mV, without decoupling capacitors. It compares well against seven LDOs designed with common gate error amplifiers for similar levels of supply voltage, output voltage and current and against seven fast LDOs employing different error amplifiers. A figureof-merit that considers the quiescent current, the maximum load current and capacitance, as well as the output voltage deviation, yielded a value for our LDO 39.8 times better than for the nearer competitor that employs common gate amplifier and 6 times better than the one employing a different error amplifier. When considering edge time and process scaling the performance of the proposed LDO is 4.8, respectively 4.5, times better than the second best in both comparisons.

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“…The return ratio is obtained by using Rosenstark's formula [17]. It does not depend on the point the loop is broken at [18]. Fig.…”

Section: B Stability Analysismentioning

confidence: 99%

LDO With Improved Common Gate Class-AB OTA Handles any Load Capacitors and Provides Fast Response to Load Transients

Răducan

Grajdeanu

Plesa

et al. 2020

IEEE Trans. Circuits Syst. I

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“…These limitations can be surpassed by using LDOs with multiple feedback loops such as those proposed in [16][17][18][19]. Stability analysis of circuits with one feedback loop is well covered by the classical feedback theory and several methods are available for deriving the phase-and gain-margins associated with the circuit return ratio [20][21][22]. Extending this approach to the analysis of circuits with multiple feedback loops is not straightforward.…”

Section: Logicmentioning

confidence: 99%

High-Precision Low-Temperature Drift LDO Regulator Tailored for Time-Domain Temperature Sensors

Răducan

Grăjdeanu

Ţopa

et al. 2022

Sensors

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This paper proposes a high-precision LDO with low-temperature drift suitable for sensitive time-domain temperature sensors. Its topology is based on multiple feedback loops and a novel approach to frequency compensation, that allows the LDO to maintain a large DC gain while handling capacitive loads that vary over a wide range. The key design constraints are derived by using a simplified, yet intuitive and effective, small-signal analysis devised for LDOs with multiple feedback loops. Simulation and measurement results are presented for implementation in a standard 130 nm CMOS process: the LDO outputs a stable 1 V voltage, when the input voltage varies between 1.25 V to 1.5 V, the load current between 0 and 100 mA, and the load capacitor between zero and 400 pF. It exhibits a DC load regulation of 1 µV/mA, a 288 µV output offset with a standard deviation of 9.5 mV. A key feature for the envisaged application is the very low thermal drift of the output offset: only 14.4 mV across the temperature range of −40 °C to +150 °C. Overall, the LDO output voltage stays within +/−3.5% of the nominal DC value over the entire line voltage, load, and temperature ranges, without trimming. The LDO requires only 1.4µA quiescent current, yet it provides excellent responses to load transients. The output voltage undershoot and overshoot caused by the load current jumping between 0 and 100 mA in 1 µs are: 10%/22% for CL = 0 and 12%/16% for CL = 400 pF, respectively. A comparative analysis against seven LDOs published in the last decade, designed for similar levels of supply voltage and output voltage and current, shows that the LDO presented here is the best option for supplying sensitive time-domain temperature sensors. The smallest thermal drift of the output offset, smaller than +/−15 mV, that is, 6.7 times smaller than its closest competitor, and the best overall performance when PSR up to 1 kHz, was considered.

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“…Op-amps are an essential component in the modern mixed-signal systems [1][2][3][4]. High-gain and high-speed op-amps can be used in the various applications such as high-resolution analogue-to-digital converters and digital-to-analogue converters, bandgap voltage references and sample-and-hold amplifiers (SHAs) [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Positive feedback technique and split‐length transistors for DC‐gain enhancement of two‐stage op‐amps

Anisheh

Shamsi

Mirhassani

2017

IET Circuits, Devices & Syst

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This study presents the design and simulation of a fully differential two-stage op-amp in a 0.18 μm complementary metal-oxide-semiconductor process with a 1.8 V supply voltage. In this op-amp, positive feedback technique and split-length transistors (SLTs) are employed to increase the DC-gain of the op-amp by about 22 dB without affecting the unity-gain bandwidth (UGBW), stability, power dissipation and output voltage swing of the conventional two-stage op-amp. A comprehensive analysis is provided for differential-mode gain, common-mode gain, power supply rejection ratio, input-referred noise, input offset, frequency response and the effect of using SLTs on DC-gain sensitivity. The proposed op-amp is utilised in a flip-around sample-and-hold amplifier (SHA). The output spectrum of the SHA shows the total harmonic distortion of 0.0023%. The post-layout and Monte Carlo simulation results show that the proposed op-amp has better performance than the state-ofthe-art designs.

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Comparative Analysis of Simulation-Based Methods for Deriving the Phase- and Gain-Margins of Feedback Circuits With Op-Amps

Cited by 6 publications

References 11 publications

LDO With Improved Common Gate Class-AB OTA Handles any Load Capacitors and Provides Fast Response to Load Transients

LDO With Improved Common Gate Class-AB OTA Handles any Load Capacitors and Provides Fast Response to Load Transients

High-Precision Low-Temperature Drift LDO Regulator Tailored for Time-Domain Temperature Sensors

Positive feedback technique and split‐length transistors for DC‐gain enhancement of two‐stage op‐amps

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