nandu said:i was simulating the noise performance of a mos diffamp, and i found that the tail mos current source contributes significantly to the 1/f noise measured at the differential output. why is this happening? i always thought the tail mos doesnt contribute to overall noise as its noise current gets evenly distributed between the 2 branches and hence gets canclled off when we view the differential output.
I see no reason why differential output noise should be a function of current source impedance. Any current in the tail should split evenly between the two transistors in the diff pair (unless they are mismatched). The output noise should be all common mode, independent of the current source impedance.tsb_nph said:Hi Nandu,
Your argument that the noise from the tail current source is common mode and hence should be rejected at the output is correct, but this rejection is based on the common mode rejection of the differentil pair, which I observe is bad because your tail current source output resistance is low - you are using short channel transistor.
Bharath
10kangstroms said:I see no reason why differential output noise should be a function of current source impedance. Any current in the tail should split evenly between the two transistors in the diff pair (unless they are mismatched). The output noise should be all common mode, independent of the current source impedance.
may i ask you how can you use cadence to run analysis about 1/f noisenandu said:i was simulating the noise performance of a mos diffamp, and i found that the tail mos current source contributes significantly to the 1/f noise measured at the differential output. why is this happening? i always thought the tail mos doesnt contribute to overall noise as its noise current gets evenly distributed between the 2 branches and hence gets canclled off when we view the differential output.
lily1981216 said:may i ask you how can you use cadence to run analysis about 1/f noisenandu said:i was simulating the noise performance of a mos diffamp, and i found that the tail mos current source contributes significantly to the 1/f noise measured at the differential output. why is this happening? i always thought the tail mos doesnt contribute to overall noise as its noise current gets evenly distributed between the 2 branches and hence gets canclled off when we view the differential output.
nandu said:what is noise up-conversion and how is it relevant to this diff-amp circuit?
nandu said:i was simulating the noise performance of a mos diffamp, and i found that the tail mos current source contributes significantly to the 1/f noise measured at the differential output. why is this happening? i always thought the tail mos doesnt contribute to overall noise as its noise current gets evenly distributed between the 2 branches and hence gets canclled off when we view the differential output.
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