LTspice IA responce

[gogoman]

hello, for fun i created this circuit and then plotted the response.  Rather than take it for granted, I like to understand the following:

1. Based on the RC, How was the filter response calculated   
2. Why does the phase start to rise at ~100k

link to tutorials will work to 

thanks

[iMo]

1. g..gle "RC transfer function calculation"
2. because there is possibly a lot of various R/L/C stuff inside the opamp model there..

[magic]

Note that you can independently plot the differential voltage at the inputs of the chip, to see what comes from your passive circuit and what comes from the chip. Or disconnect the chip and see if its input admittance is having any effect.

The stuff at high frequencies may be some input to output capacitance in the chip (or in the model, at least). An example of such effect is base-collector capacitance of simple common emitter amplifiers, which sometimes "overrides" normal operation of the stage and passes very high frequency signals at almost unity gain, uninverted.