ADA4625-1 LTspice Model Offset Voltage

Question

Hello, 
 when simulating ADA4625-1 configured as simple unity gain buffer in LTspice with single 5V supply (Vs- =0, Vs+=5V), I get a systematic DC offset of -45.406mV which is far beyond the max value in the datasheet (+/- 1mV max). Is there a problem with the (LT)Spice model? 
 Thank you 
 Francois Dorel

Hooman · Answer

Hi Francois, 
 Try simulating the ADA4625-1 unity gain buffer with dual supplies instead. With a single supply, with input tied to ground, the output won't be able to swing all the way to ground and shows up as an offset at the output. Here you see the output is only 33nV: 
 
 ADA4625-1 dual supply buffer 7_5_21.asc 
 Regards, 
 Hooman

Hooman · Answer

Hi Francois, 
 I just noticed that you and I both may have been misled somehow on "Low supply" voltage operation. Keep in mind that the input Voltage range requires 3.5V headroom to V+. If you look at 5V operation table (datasheet page 5), you'll notice that the highest input voltage is 1.5V with 5V single supply (3.5V headroom). When you observe this limitation, the simulated output offset voltage is in the uV range which is correct. 
 So, I'd like to confirm with you that you also agree that it's the input voltage range condition that may have caused us to doubt the model. For now, I'll retract my comment about the model having issues at low supply voltage and instead attest that the model does not seem to have this offset issue we originally thought it does. 
 In this simulation, I've shifted the V+ and V- supplies such that there is 4V headroom from the input CM voltage to the V+ supply, and you can see that the output is very near 0V: 
 
 ADA4625-1 dual supply buffer Vs=+-2p5V 7_7_21.asc 
 
 Regards, 
 Hooman