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Hybrid cascode compensation with Q-factor control module for three-stage OTAs driving ultra-large load capacitors
Circuit World ( IF 0.9 ) Pub Date : 2020-08-06 , DOI: 10.1108/cw-03-2020-0036
Hamed Aminzadeh , Mohammad Mahdi Valinezhad

Purpose

The purpose of this study is to discuss the effect of hybrid cascode compensation with quality factor (Q-factor) control module for the three-stage amplifiers driving ultra-large load capacitors. Compared to the present frequency compensation solutions, it extends the amplifier bandwidth by establishing an extra AC feedback pathway besides the primary pathway through the Miller capacitor, increasing the loop gain at the gain–bandwidth product (GBW) frequency by pushing to the higher frequencies the nondominant poles.

Design/methodology/approach

A Q-factor control block is used to improve the damping factor of the compensation loop with no power or area overhead, thereby reducing the frequency peaking and the undesired oscillation in the time response for small load capacitors. The Q-factor control module is realized by a tiny-size on-chip capacitor, and provides an extra feedback loop to feed the damping current back to the input stage. A left-half-plane (LHP) zero is also introduced to further improve the stability.

Findings

A prototype of the proposed amplifier is simulated in 180-nm CMOS with a quiescent current of 24-µA from 1.80-V voltage supply. It achieves a 3.98-MHz gain–bandwidth product for 500-pF load capacitor, while the overall compensation capacitor is limited to 0.5-pF and the DC gain is extended beyond 100-dB.

Originality/value

The proposed amplifier is absolutely stable for the load capacitors ranging between 80-pF and 100-nF.



中文翻译:

带有 Q 因子控制模块的混合级联补偿,用于驱动超大负载电容器的三级 OTA

目的

本研究的目的是讨论具有品质因数(Q-factor)控制模块的混合共源共栅补偿对驱动超大负载电容器的三级放大器的影响。与目前的频率补偿解决方案相比,它通过在通过米勒电容器的主要通路之外建立额外的交流反馈通路来扩展放大器带宽,通过推动更高的频率来增加增益带宽积 (GBW) 频率处的环路增益非优势极点。

设计/方法/方法

Q 因子控制块用于在没有功率或面积开销的情况下提高补偿回路的阻尼因子,从而减少小负载电容器的时间响应中的频率峰值和不希望的振荡。Q 因数控制模块由一个微型片上电容器实现,并提供一个额外的反馈回路将阻尼电流反馈回输入级。还引入了左半平面 (LHP) 零以进一步提高稳定性。

发现

建议放大器的原型在 180-nm CMOS 中模拟,静态电流为 24-μA,来自 1.80-V 电压电源。它为 500pF 负载电容器实现了 3.98MHz 的增益带宽积,而整体补偿电容器限制为 0.5pF,DC 增益扩展到 100dB 以上。

原创性/价值

建议的放大器对于 80-pF 和 100-nF 之间的负载电容器绝对稳定。

更新日期:2020-08-06
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