| Citation: |
Hu Jingjing, Huijsing J H, Ren Junyan. A Three-Stage Operational Amplifier for a Wide Range of Capacitive Loads[J]. Journal of Semiconductors, 2007, In Press.
Hu J J, Huijsing J H, Ren J Y. A Three-Stage Operational Amplifier for a Wide Range of Capacitive Loads[J]. Chin. J. Semicond., 2007, 28(11): 1685.
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A Three-Stage Operational Amplifier for a Wide Range of Capacitive Loads
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Abstract
This paper presents a three-stage CMOS operational amplifier (opamp) that combines accuracy with stability for a wide range of capacitive loads.A so-called quenching capacitor is added to a multipath nested Miller compensation (MNMC) topology to obtain stability for a wide range of capacitive loads.Theoretical analysis and mathematical formulas are provided to prove the improvement in stability.A prototype of this frequency compensation scheme is implemented in a 0.7μm CMOS process.Measurements show that the amplifier can drive capacitive loads ranging from 100pF to 100μF with a gain of 90dB and a minimum phase margin of 26°.The amplifier has a unity-gain bandwidth of 1MHz for a 100pF capacitive load.It employs a quenching capacitance of 18pF. -
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