How do I add two high speed analog voltages?
Sure it's possible - easy, even. Let's assume your source impedance (which you didn't mention) is &lt; 10 ohms, and lets assume that your signal amplitude (which you also didn't mention) is &lt; 5 volts, and that your load impedance (which you didn't mention) is > 1k. Then







simulate this circuit &ndash; Schematic created using CircuitLab

will work fine. You may (will) need decoupling caps and possibly a feedback cap for stability, but otherwise you should be fine.