Re: Offset voltage on voltage follower

From: Jonathan Kirwan (jkirwan_at_easystreet.com)
Date: 08/19/04 

Date: Thu, 19 Aug 2004 20:40:19 GMT

On 19 Aug 2004 19:05:09 GMT, cfoley1064@aol.com (CFoley1064) wrote:

>Summing Op Amp Level Shifter
> Vin(0-5V)
> ___
> o-|___|-o---.
> 2K | |
> 3K.-. | .----------.
> +5V | | | | VCC |
> + | | | | + |
> | '-' | | |\| |
> .-. | | '---|-\ |
>18K| | === | ___ | >---o
> | | GND '-|___|--o---|+/ Output (0.5V to 3.5V)
> '-' 33K | |/|
> | ___ | VEE
> o----------|___|--'
> | 33K
> .-.
> 2K| |
> | |
> '-'
> |
> ===
> GND

This looks wrong. It boils down to:

                34.2k
0-3V V1 O-----/\/\/----,
                         |
0.5V V2 O-----/\/\/----+-----> V3, to opamp + input
                 34.8k

That should yield:

    V3 = (V1*34.8k + V2*34.2k) / (34.2k+34.8k)
       = 247.83mV + 0.50435*V1

at the + input. I'd tend to guess, then, that the output would vary from about
245mV to about 1.76V.

Not quite the desired 0.5 to 3.5V.

Jon

Relevant Pages

  • Re: Offset voltage on voltage follower
    ... >>Summing Op Amp Level Shifter ... >> GND ... It boils down to: ... > That should yield: ...
    (sci.electronics.basics)
  • Re: wanting advice on starting a home business
    ... The longer I watch, the better I describe. ... Sometimes better descriptions yield better results. ... What it all boils down to is how I feel about a particular title and what I ask for it. ... I find that people will pay whatever I ask as long as it's not outrageous or out of line with what other people are asking. ...
    (alt.marketing.online.ebay)