Re: Questions about AD831

Hi Julio,

Assuming a 50 Ohm load impedance on the IF connector in Figure 2, then a 1:1 balun would reflect a 50 Ohm differential load impedance across the balun, and then it would be 25 Ohms single-ended.  So Rc = 25 Ohms, Re = 20 Ohms, and 1/gm = 1.44 Ohms with 18 mA of DC current, yields a gain of about 1.16, which is pretty close to unity gain.  Remember these are approximate numbers off of an idealized schematic.

Thanks,

Joel