I'm only aware of one company that makes an amplifier designed to amplify both electric and acoustic guitars; it is Rivera whose three Sedona models are designed for both. They are expensive however.
http://www.rivera.com/index.php/products/combos/142
The demands of an electric guitar and a pickup equipped acoustic guitar are very different so with the exception of the Sedona, a majority of acoustic guitarists would only be satisfied with an amp designed specifically for a acoustic guitar amplification and most electric guitarists would only settle for an electric guitar amp.
Electric guitar amps have a limited frequency response, high distortion and are designed to add
tone (
color). An acoustic guitar needs a wider frequency response that is flat (
uncolored), low distortion and a wider dynamic range.