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Vitamin-C
Joined: 06 Apr 2004
Posts: 43
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 30 Jul 2004 10:19 Audio sigma delta ADC |
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Hi,
What things should be considered when design audio codec
with sigma delta ADC ?
What is the requirement of the opamp for example ?
thanks
vita
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opamp741
Joined: 17 Jun 2004
Posts: 145
Helped: 10
Location: India
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| 30 Jul 2004 11:31 Re: Audio sigma delta ADC |
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idle tones should not be there.
u can find the reason behind idle tones and the solution in the books.
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bear7679
Joined: 18 May 2004
Posts: 136
Helped: 21
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| 02 Aug 2004 1:23 Re: Audio sigma delta ADC |
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| The most important thing about the OPAMP is the settling time and noise. The major noise source is 1/f noise.
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Vitamin-C
Joined: 06 Apr 2004
Posts: 43
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| 02 Aug 2004 4:13 Re: Audio sigma delta ADC |
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Thank you.
What opamp architecture is good ?
How about cascode (with gain-boost) for a 3V supply?
any suggestion,
Vita
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opamp741
Joined: 17 Jun 2004
Posts: 145
Helped: 10
Location: India
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| 02 Aug 2004 6:56 Re: Audio sigma delta ADC |
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| Opamp gain can be decided as 4 or 5 times of ur oversampling ratio..now it depends on ur technology that which topology will give u suitable gain..Casacode architecture will limiti ur opamp swing means ur integartor will saturate will quickly..keep all this tradeoffs in ur mind when selecting any architecture..
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kyrandia
Joined: 23 Jun 2004
Posts: 34
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| 03 Aug 2004 4:54 Re: Audio sigma delta ADC |
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| try to use folded cascode opamp . I think you don't need gain boost in audio sdm
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bear7679
Joined: 18 May 2004
Posts: 136
Helped: 21
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| 04 Aug 2004 1:11 Re: Audio sigma delta ADC |
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| You can use telescope opamp if the dynamic range of the opamp's output is not large.
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Vitamin-C
Joined: 06 Apr 2004
Posts: 43
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| 04 Aug 2004 11:46 Re: Audio sigma delta ADC |
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thank you
If I implemented in folded cascode, I need a
switch capacitor common mode feedback.
Does any one know how to simulate the AC response
with switched capacitor common mode feedback which
have two clocks input signal ??
thx in advance,
Vita
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bear7679
Joined: 18 May 2004
Posts: 136
Helped: 21
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| 04 Aug 2004 12:02 Re: Audio sigma delta ADC |
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| I use resistor to replace the switch & capacitor, that means I use RC common mode feedback circuit in the ac analysis.
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kyrandia
Joined: 23 Jun 2004
Posts: 34
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| 05 Aug 2004 2:39 Re: Audio sigma delta ADC |
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| SpectreRF can deal with your problem, Try to use pss and pac analysis.
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Vitamin-C
Joined: 06 Apr 2004
Posts: 43
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| 05 Aug 2004 4:50 Re: Audio sigma delta ADC |
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thanks for information
If possible could you show me an example how
to simulate a switched cap. circuit in SpectreRF.
I only used Hspice before, is the SpectreRF syntax very similar to Hspice ?
thank you.
Vita
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emilian6
Joined: 14 Oct 2004
Posts: 13
Location: UGent/Belgium
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| 14 Oct 2004 17:42 Re: Audio sigma delta ADC |
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You can look at this guide:
http://www.designers-guide.com/Analysis/sc-filters.pdf
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devrimaksin
Joined: 13 Oct 2004
Posts: 93
Helped: 9
Location: Dallas, Texas, USA
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| 15 Oct 2004 3:30 Audio sigma delta ADC |
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Things to be considered for sigma-delta modulator design:
1. Sistem level
a) Signal Transfer function
b) Noise transfer function
c) Stability analysis if necessary
d) Sensitivity of these transfer functions to the system parameters.
2. Circuit Level
a) OPAMP Settling time
b) OPAMP Finite DC Gain
c) OPAMP SlewRate
d) OPAMP noise
e) Switch On-resistance effect
f) Path Mismatch
g) Integrator Mismatch
h) If it is multi-bit Dynamic Element Matching and
DAC nonlinearity
i) Noise sensitivity of different nodes
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