Designing CMOS folded-cascode operational amplifier with flicker noise minimisation

A <inline-formula> <tex-math notation="TeX">$g_{m}/I_{D}$</tex-math></inline-formula>-Based Noise Optimization for CMOS Folded-Cascode Operational Amplifier

“…It can be shown that i 2 nd,th , the thermal noise at the drain terminal, is [2] i 2 nd,th = 4kT γg m (1) where k is the Boltzmann constant, T is the temperature in Kelvin, g m is the transconductance, and γ is the bias-dependent noise parameter. According to this model, γ approaches 1 when the drain-to-source voltage (V DS ) approaches zero and decreases to 2/3 when the device enters the saturation regime [2].…”

“…where K f is a process parameter that depends on the W and L of a transistor [1], C ox is the oxide capacitance, W is the width, and L is the length. At the device noise corner frequency (f co ), the thermal noise is equal to the flicker noise…”

“…Since flicker noise is inversely proportional to the gate area, large transistors are frequently used to minimize flicker noise. A strategy for minimizing noise without increasing the gate area excessively was developed for a folded-cascode amplifier by Chan et al [1] in a 0.8-μm CMOS. A design equation that accounts for the gate-area-dependent flicker noise coefficient (K F ) was proposed [1].…”

“…A strategy for minimizing noise without increasing the gate area excessively was developed for a folded-cascode amplifier by Chan et al [1] in a 0.8-μm CMOS. A design equation that accounts for the gate-area-dependent flicker noise coefficient (K F ) was proposed [1]. In nanoscale CMOS, in addition to K F , the effective mobility also depends on the bias of a transistor [2].…”

A Low-noise Low-offset Op Amp in 0.35&#x003BC;m CMOS Process

“…Having g m4 smaller than g m2 to reduce noise also helps reduce the second term in (14). The overdrive voltage V ov1,2 which is designed to be a small value helps minimize the last term [8] in (14). Having a large size for the input pair reduces the standard deviation of the difference between the input pair's thresholds [10].…”