Recently I have been working with the Analog Devices AD797 op-amp in LTspice, and have been getting poor performance from the amplifier when using a low-amplitude signal. This is my circuit in LTspice:
The voltage source I am using is a sine wave at 40KHz with amplitude of .125 V, parallel capacitance of 3.4nF and series resistance of 4KΩ. I am trying to mimic the hydrophone that this circuit will eventually be an amplifier for, so these numbers aren't random. Also, I have set the gain of the amplifier so high because this circuit will eventually need to amplify voltages much lower than .125 V. I believe my problem is with the blocking capacitor / highpass filter I use on the output of the voltage source. Vin is consistently lower than the amplitude of the voltage source and V2 looks identical to Vin, except it has been shifted negatively by a few millivolts. The following screenshots are what I see in LTspice when simulating the circuit.
The second image include the output of the amplifier, which reflects this negative shift of the input signal. I am a relative beginner, and my understanding of reactive circuits is shaky. Any help with eliminating / minimizing this negative shift between Vin and V2 would be much appreciated. Thanks
Here is a link to the AD797 datasheet.