Post Go back to editing

ADA4522 Spice model Input Bias Current Too high

LTSpice XVII - date installed 2017

I’m measuring about 12 nA for input bias current. The data sheet gives room typical and max of 50 and 150 pA respectively. The max over temperature (125C) is spec’d at 3 nA.

My simulation is a simple non-inverting unity gain buffer with a feedback resistor from Vout to the 4522 (-) input. The (+) input is tied directly to an input DC voltage source set to zero volts (negative side of input source is tied to cut com. The 4522 is powered by +/- 12 VDC.

The circuit behaves like I would expect. When the feedback resistor is set to zero ohms, the output goes to about 1uV. When I set the resistor to 1 Meg, the output goes to about -12 mVDC which means there is about 12 nA coming out of the (-) input of the 4522. The current in the .op table shows the Ibiza’s current as about 12 nA.

Has a newer Spice model been developed that works more like the real part?

Parents Reply
  • Hi,

    Select in the LTspice library, ADA4522-1 model and add its symbol on your test circuit.

    If you opt to use the one in the web, download the cir file. To easily use it and associate it in a symbol without problems, add "opamp2" symbol from the library and rename it with the subckt name of the model you downloaded e.g. ADA4522. Then click "s" and add the command .lib <directory path where your downloaded cir is located> and run the simulation.

    I supposed you selected ADA4522 model in the library? It will not work because it's model was already removed from the library. I'm confused on what particular model and symbol you used in your test ckt. The model seems it is ADA4522-1 but your symbol is ADA4522. There might be some mismatch going on your test circuit, the reason you are getting erroneous results.