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Why are ro1 and ro2 modeled in parallel here? (Read 3666 times)

baab Senior Member Offline Posts: 178 EA	Why are ro1 and ro2 modeled in parallel here? Oct 06^th, 2013, 2:28am Hi, I am reading about Noise in �Design of Analog CMOS Integrated Circuits Behzad Razavi. Please help me with this question. Thank you.
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raja.cedt Senior Fellow Offline Posts: 1516 Germany	Re: Why are ro1 and ro2 modeled in parallel here? Reply #1 - Oct 6^th, 2013, 4:06am Correct... To calculate noise 1. Drwa small signal picture 2. Add one transistor noise (could be current or voltage) 3. Find the output voltage/current. Thanks, Raj.
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baab Senior Member Offline Posts: 178 EA	Re: Why are ro1 and ro2 modeled in parallel here? Reply #2 - Oct 6^th, 2013, 4:50am Thank you for the confirmation.
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aaron_do

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Re: Why are ro1 and ro2 modeled in parallel here?
Reply #3 - Oct 7^th, 2013, 5:51pm

Hi baab,

Quote:

because the transistors are operating in saturation, and so noise can be considered as small-signal

the transistors don't need to be operating in saturation for the noise to be considered small. Noise is usually a small signal. If it wasn't then you would have a tough time detecting your signal inside the noise...

regards,
Aaron

there is no energy in matter other than that received from the environment - Nikola Tesla

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