The op amps form the most important analog part of the SSMU - the magnitude and phase measurements of a sine wave (the Bode plot circuits). They also amplify the DAC output for the device/circuit under test.

I first determined what kind of slew rate I would need. While I planned for a maximum output voltage of 15V, I initially relaxed this down to 9V to make sure I wasn't filtering out any op amps with compelling specs or prices. There are two main frequencies of interest - 20kHz and 100kHz. The first is the required max for audible sound and the second is the cutoff I picked so a filter at 100kHz would do a decent job of attenuating the DAC switching frequency. This calls for a slew rate of 1.88-9.42V/us for 15V max or 1.26-6.28V/us for 9V max.

Next I looked at the errors introduced by input offset voltage and input bias current. With a 12bit ADC at 3.3V, 1LSB = 0.806mV. There are about 4 op amps cascaded in the Bode plot circuit (1 with up to 5V/V gain).

Finally, I needed a supply rail up to 9-15V at a reasonable price. Based on these points I've currently picked the MAX44252. It comes in a quad package for $2.64 and while it doesn't quite have the 15V slew rate for 100kHz (8V/us) it does have a pretty good input offset voltage (3-6uV) and input bias current (200pA).