Virtual GND OPA336 question.

[drumanart]

Virtual GND question.
Hello, I made a small preamp using an OPA336. The circuit is powered with 3V
and to test the circuit I use a Wave-Generator with 600 Ohm output impedance.
Here is the schematic:



If I connect a Square-Wave (1kHz, 100mV) and watching the output with an
Oscilloscope, I see that the circuit has a very poor performance. The
Square-Wave locks like a Triangle-Wave and even a Sine-Wave with 1,5KHz is
far under 3dB.
I’m pretty sure that I designed something wrong with the Virtual GND.
Does any body have experience with the OPA336n or OPA2336?

 

[godfreyl]

The virtual earth looks fine, but the opamp is very slow. Maximum slew rate is 0.03V/us typical. Even so, that should be enough to give a 2V pk-pk sine wave output up to about 4.7KHz. If it's for audio, I'd want a much faster chip.

edit: Wait... what?!
I just read some more in the datasheet - the GBW is only 100KHz typical, so your frequency response will roll off at about 9KHz, and distortion will probably be bad since the feedback factor will be very low over most of the audio band.

 

[drumanart]

The virtual earth looks fine, but the opamp is very slow. Maximum slew rate is 0.03V/us typical. Even so, that should be enough to give a 2V pk-pk sine wave output up to about 4.7KHz. If it's for audio, I'd want a much faster chip.

edit: Wait... what?!
I just read some more in the datasheet - the GBW is only 100KHz typical, so your frequency response will roll off at about 9KHz, and distortion will probably be bad since the feedback factor will be very low over most of the audio band.

Right, I have to look more carefully to the data-sheet. I try to do a design with the MAX4475, it seems to by a good ic for audio.
Thanks for the advise Martin