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Why is CMOS noisy?

8/17/1996 6:20 PM
Erik M. Wood
Why is CMOS noisy?
Howdy do!  
I've heard many of you mention in posts that CMOS chips are noisier than other types of ICs. I've also seen this in several reviews of CMOS based distortion pedals. Why is this? Is there some construction method which causes this? Is it a design flaw? I don't suppose it would be a flaw, per se, because of the digital nature of the chips. Some noise would not seem to affect performance so long as it did not approach the "High" state of the chip. Or, is the noise simply caused by a flaw in the design of the circuit which employs the chip (not properly grounded, static electricity, etc...)? I have not heard any similar complaints about other MOSFETs in general, so I am not sure what to think. Can anyone shed some light on this?  
8/17/1996 6:23 PM
CJ Landry

This is sort of an answer to your previous message about the HOT Tubes Distortion. The CMOS inverters, CD4049, are operating in a linear manner which is not how the mfg spec'ed them to operate.  
Basically, the inverters are a digital chip placed in an analog environment. Without building the circuit this is a hard one to theorize. However, you got me interesrted and I am going to build it soon. I"ll get back to you with more data.  

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