Clement wrote:
>
>Hi,
>
>Actually, I mistype couple of the requirements on my previous question. =
>The signal is vary from -400mv to +1100mv, not -40mv to +1100mv. So, I =
>need to shift it +400mv (0.4Volt). Now, the new adjust range should vary =
>from 0 to 1500mv (1.5Volt). After a gain of 3.33, it would give me an =
>analog singal vary from 0 to 5volt and I can read it using A/D.  The =
>question is how can I add 0.4Volt offset to my signal?  And I don't have =
>any negative voltage available. The signal is from a temperature sensor. =

In your first post you mentioned passing the signal thru an op-amp to boost
the 1.5Vpp signal to 5Vpp.  If you can afford for the signal to be inverted
you can try this:
                                  3.333K
                             ----/\/\/\---------|
                             |                  |
                             |                  |
                             |     |\           |
                   1K ohm    |     | \          |
        Vin >-----/\/\/\-----0-----|  \         |
        -0.4/1.1                   |   \________|_______\ Vout
                        +5V  |-----|   /                / 5.0/0.0
                         |   |     |  /
                        /    |     |/
               4582 ohm \    |
                        /    |
                        \    |
                        |    |
           0.89576V     0----|
                        |
                        /
                        \
                        /
              1000 ohm  \
                        |
                        |
                     ------
                     / / /


Of course most op-amps require negative voltage.

Hello, I must be going...

Michael

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