Hi everyone
I need a sine wave generator preferably using the TL 071 opamp. I will accept any frequency from 100 hz to 10 Khz , supply voltage can be from 5volt to 18 volt. I have tried to simulate several designs, including the wien bridge, and twin t and phase shift, with no results. I would prefer to use the phase shift design. I would also prefer to use the spit supply design using positive, negative, and zero. First of all I’m using Circuit Maker to simulate the designs which does not have the TL071 in the library. I know that using the inverted input of the opamp will give me 180 deg. Phase shift at the output, then this is fed through another RC network for the other 180 deg , but to calculate the RC values for the other 180 deg and to consider the gain of the amp is where I’m having the problem. The circuit below is the one which I have been simulating. Can anyone help with the design or the formula or an opinion? Thanks

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not working.JPG (14.9 KB, 27 views)

 

Your inverting amplifier has a very low input impedance of only 2k ohms so it loads down the circuit so much that it doesn't work. If you add a non-inverting opamp ahead of the inverting one then it will have a high input impedance with low loading. If you add an opamp after each RC stage then there will be much less loss and the calculated frequency won't have a high error. Look at this Sine-wave Oscillators document from Texas Instruments:

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Phase-shift oscillator.gif (25.4 KB, 23 views)

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sine-wave oscillators TI.pdf (253.8 KB, 10 views)

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Uncle $crooge

 

Thanks audioguru
I got the simulation to work. I have been fighting with it for a whole day. Part of the problem was as audioguru pointed out (thanks so much) and the other was the software “ circuit maker”.
A big note on “circuit maker” is that if you do not add a signal generator to the design, the software will not show traces on the oscilloscope. You also have to ground the signal generator.

 

Here is a circuit a built sometime ago, I just checked it to see if it was still working. The calculate frequency is 146 Hz, actual frequency is 144 Hz. It has a little distortion on the peak of the negative cycles. That would go probably go away if the RF=29R.
It was originall built with a 741 op amp, but I tested it with the TL081, so it should work with a TL071.

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PHASE SHIFT OSC..JPG (31.5 KB, 16 views)

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The great thing about electronics is unlimited ways to do the job. The only limit is one\'s imagination. I generally think my way is best.
Show me a different way. I have an open mind.

 

A TL071 is a TL081 that is selected for low noise. Their spec's are exactly the same.

A lousy old 741 opamp should be buried.

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Uncle $crooge