using the opamp of a sigma delta A/D

[John]

November 19, 2004

Hi all,

I am interfacing the MSP430 with an external 24 bit A/D (ADS1242). I
really need 19 to 18 bit of resolution. I was wondering if it is
preferable to use the internal amplifier of the A/D or to amplify the
signal externally.

Thanks,
John

 

[Winfield Hill]

John wrote...

I am interfacing the MSP430 with an external 24 bit A/D (ADS1242).
I really need 19 to 18 bit of resolution. I was wondering if it is
preferable to use the internal amplifier of the A/D or to amplify
the signal externally.

What internal amplifier of the A/D was that?


--
Thanks,
- Win

 

[John]

Nov. 22, 2004

Hi all,

Thank you for the response to my email. When the gain was less than
4.0 the output to the input ratio was close to the gain but when I
increased the gain the output to input ratio was much lower than the
gain and I am not sure why? I am not sure if I was doing something
wrong or others had the same experience. If so, why?

Thanks,
John.



Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote in message news:<o5q3q0hl0n308qv8740dsdun9tacmtgiqi@4ax.com>...

On 21 Nov 2004 22:44:06 -0800, the renowned eeaj2002@gmail.com (John)
wrote:

November 19, 2004

Hi all,

I am interfacing the MSP430 with an external 24 bit A/D (ADS1242). I
really need 19 to 18 bit of resolution. I was wondering if it is
preferable to use the internal amplifier of the A/D or to amplify the
signal externally.

Thanks,
John

Why wouldn't you want to use the internal PGA? Is your input range
much less than your reference voltage?


Best regards,
Spehro Pefhany