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3rd harmonic in adc simulate

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tuza2000

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when i simulate the flash adc use ideal resistor,
the 3rd harmonic is -43dB
but when i change it to tsmc 0.18 rnploy resistor,the 3rd harmonic turn to -36dB
how and why?

what should i do to optimize it ?
 

hi
if there is non linear effect in resistor model. harmonic amplitude can change.
optimization?
do you want to optimize circuit ?
you can use optimization method that exist in ads.
 

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    tuza2000

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i want to know how can i do to reduce the 3rd harmonic

what's the optimization method exist in ads?
 

hi
ads and APLAC have many optimization algorithm such as genetic algorithm, simulated annealing, down hill simplex, DERIVATIVE method and ...
you can use hspice and matlab to optimize your circuit.
 

I suggest you check the model file provided by TSMC: the actual resistor model may include voltage coefficients to model non-linear characteristic of poly resistor. It may also include the parasitic capacitance in the resistor model, which will affect your resistor string settling and shown as 3rd-order distortions. I don't think there is any 'optimization method' provided by EDA tools which can reduce this HD3 -- it is just too good to be true :) On the other side, solving this linearity problems certainly demonstrates the value of a good analog design engineer.
 

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