I require the THS4531A to have a low noise output at DC. The datasheet suggests using a 220nF capacitor on the Vocm pin to reduce noise.
I tried a simulation in TINA using a unity gain configuration (4.7kilohm resistors, 5V supply) and found the total noise for the 0.1 to 10 Hz band to be a very large 289 microvolts rms. Although increasing the capacitance reduced the noise, it wasn't until the Vocm pin was connected to a 2.5V battery (this being the desired output common mode voltage) that the simulator predicted a very reasonable 395nV rms.
My question is whether it is necessary to drive the Vocm pin with a low impedance, low noise voltage source to get low noise at dc or is the TINA simulation overly pessimistic regarding low frequency noise ?