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There are two theories behind the physical origins of 1/f (flicker) noise: Hooge's mobility fluctuation theory, and McWhorter's carrier density (or number fluctuation) model. The number fluctuation model is based on the random trapping and release of mobile carriers in traps located at the Si-SiO2 interface of a MOSFET.hmsheng said:Why it is believed that PMOS devices exhibit less 1/f noise than NMOS transistors?
Chopping and auto-zeroing are useful techniques for handling 1/f noise in amplifier circuits (**broken link removed**).mitrobge said:i/f noise is inversely proportional to WL. Increase of WL decreases flicker noise. Is there any other techniques to deal with the issue?
What is your definition of "near DC?" Some people consider 500KHz to be a low frequency, whereas others are focused on the audio band of 20Hz - 20KHz. The simulators are reasonably good, but the real problem is getting the fab to characterize the 1/f noise model parameters properly. Most fabs are too lazy to do it properly, so your simulations give you inaccurate results.How accurate are the simulators regarding the noise in very low frequencies near dc?
hmsheng said:Why it is believed that PMOS devices exhibit less 1/f noise than NMOS transistors?
roadbuster said:There are two theories behind the physical origins of 1/f (flicker) noise: Hooge's mobility fluctuation theory, and McWhorter's carrier density (or number fluctuation) model. The number fluctuation model is based on the random trapping and release of mobile carriers in traps located at the Si-SiO2 interface of a MOSFET.hmsheng said:Why it is believed that PMOS devices exhibit less 1/f noise than NMOS transistors?
In a PMOS device, the mobile carriers (holes) move in a "buried channel" rather than right along the oxide-silicon interface. Since the carriers are distanced from the traps in the gate oxide, the 1/f noise is reduced.
However, reduced 1/f noise is not consistently observed in PMOS vs. NMOS devices on the same process. I have seen plenty of process data sheets which show 1/f noise of the PMOS and NMOS devices to be the same. On one process I recently used, the PMOS devices had worse 1/f noise than the NMOS devices.