There is no chart that shows the output impedance in the datasheet. However, there is a plot for both, s11 and s22. Zout is calculated from s22 the following way: Zout = Z0*((1+s22)/(1-s22)). Z0 is assumed to be 50 ohms. If we assume that this plot was recorded with the ADA4930 connected the same way as for the preceding crosstalk/balance measurement (Fig. 40), then you have to subtract the series connected 50ohms output resistor to get the output impedance. For example, at 100MHz, the s22 is -30dB, which means 0.0316 (10^(-30/20)). This leads to an ouput impedance of 53.27 ohms less 50 ohms = 3.27Ohm!

Hi Roger

There is no chart that shows the output impedance in the datasheet. However, there is a plot for both, s11 and s22. Zout is calculated from s22 the following way: Zout = Z0*((1+s22)/(1-s22)). Z0 is assumed to be 50 ohms. If we assume that this plot was recorded with the ADA4930 connected the same way as for the preceding crosstalk/balance measurement (Fig. 40), then you have to subtract the series connected 50ohms output resistor to get the output impedance. For example, at 100MHz, the s22 is -30dB, which means 0.0316 (10^(-30/20)). This leads to an ouput impedance of 53.27 ohms less 50 ohms = 3.27Ohm!

Hope my assumptions are all correct!

Cheers...