Op amp sine wave generator puts DC level on output...why?

[Flyback]

Thanks, ....how about the problem i am having here with a DC level appearing in the sine wave output of a filtered square wave circuit?.........................

I have produced a 50KHz sine wave by filtering a 5V, -5V square wave in LTspice.

Despite the output being capacitively coupled, the output sine wave has managed to acquire a DC level of 70mV…….the input square wave has an input DC level of 0mV.

How has the sine wave got this DC level?…here is the schematic….(its also attached )


Schematic
https://i49.tinypic.com/2953lom.jpg

Here is the output sine waveform, showing its been “Lifted”….

Output waveform
https://i45.tinypic.com/wi4ag.jpg


Here is the LT1006 op amp datasheet:
https://www.electro-tech-online.com/custompdfs/2013/01/1006fa.pdf

simulation also attached.

 

[MikeMl]

Same comment as yesterday: What a horribly complicated circuit just to get a 50KHz sine wave.

The problem is the size of your coupling caps. Remove C4 and C5 (not needed). Make C6 about 10n. The time constant of the inter-stage coupling is ~1sec, so you would have to simulate for several seconds for the output to settle to its steady state (no DC component).

You could get a better low pass filter in one op amp stage than this. You could also get a low-distortion 50kHz sine wave directly, with no filtering required.

Learn how to post a real simulatable .asc file.