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Design >> Analog Design >> Low frequency noise in current to frequency converter
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Message started by rajivs1001 on Jul 22^nd, 2009, 2:38pm

Title: Low frequency noise in current to frequency converter
Post by rajivs1001 on Jul 22^nd, 2009, 2:38pm

I am working on current to frequency converter which consists of following two circuits

1- Integrator circuit which integrates the current. In the beginning output of this stage is RESET to ground (0V) and then because of current integration, output of integrator starts rising.

2- Output of integrator goes to a comparator which compares this voltage with a reference voltage and as soon as output of integrator becomes equal to this reference, comparator output toggles and RESET the integrator.

What I see is very high level of noise at low frequencies. Can someone please suggest some reference for understanding the root cause of this type of noise better.

Any suggestion/comment with be very useful.

Thanks,
Raj

Title: Re: Low frequency noise in current to frequency converter
Post by raja.cedt on Jul 22^nd, 2009, 9:28pm

hi,
can you give your schematics, because with the info what you have for me it seems like there equal probability of getting noise from both (comp and integrator)..you can try this architecture also..First integrate the current and then use ring oscillator...this will give same result but i don't know about noise which it gives

Thanks,
Rajasekhar.

Title: Re: Low frequency noise in current to frequency converter
Post by thechopper on Jul 24^th, 2009, 8:47pm

IF the input current noise is white, after integration will have 1/f^2 profile and therefore more noise power at lower frequency.
This is normal for any integrator processing white noise at its input....

Tosei