TL072: 90 degree phase shifter

HARI T O1

Part Number: TL072

Tool/software:

Dear Team,

I have a sine wave of amplitude 1V and it's frequency varies from 5Khz to 50Khz. I need to design a circuit which will phase shift this sine wave by 90

without changing the amplitude.

I found a solution here using all pass filter.In this 3 all pass filters are cascaded

Below is the value of filter R and C from the tool mentioned above.

My circuit is given below.

when the frequency is 50khz I am almost getting 90 degree phase shift.O/P waveform is given below

But when the I/P is 5Khz my out is 180degree out of phase

May I know how to solve this.or please tell me if you have any better circuit ideas.

Phase_Shif.TSC

My circuit is attached along with this.

Regards

HARI

over 1 year ago

0 Raymond Zhang1 over 1 year ago

TI__Guru* 77501 points

Hi HARI,

You seem to have to tool to generate the errors in the all pass filter. That is what I would do.

Have you tried 4 stages all pass filter, it may work out better than 3. In addition, the frequency range is a bit wide, so I will optimize the circuit in the middle between 5kHz and 50kHz and see if it would have better transition in phase shift. One of the resistor in RC shift may require to be potentiometer, if you want keep the phase shift more accurate.

Please let me know if you have other questions.

Best,

Raymond

0 HARI T O1 over 1 year ago in reply to Raymond Zhang1

Expert 1675 points

Hi Raymond,

Below is the block diagram of my system.

I have a sine wave of frequency 5Khz to 50khz. I need an output which is 90 degree phase shift of the input without change in amplitude

Regards

HARI

0 Raymond Zhang1 over 1 year ago in reply to HARI T O1

TI__Guru* 77501 points

Hi HARI,

Please try the following.

You have the tool to simulate this, so it is easier to generate from the tool and analyze the error. I have to do it by hand. One of the stage, you may need to put potential at the last stage for fine turning. The BW is a bit wide and too much R and C variations and I can not guarantee that is going to work smoothly.

1362.TL072 All Pass Filter 90 4 stages 03262025.TSC

Best,

Raymond

0 HARI T O1 over 1 year ago in reply to Raymond Zhang1

Expert 1675 points

Hi Raymond,

Thank you.

Will this circuit give constant phase shift of 90 degrees for the entire frequency range(5k to 50K)

0 Raymond Zhang1 over 1 year ago in reply to HARI T O1

TI__Guru* 77501 points

Hi HARI,

I only checked 3 points at 5kHz, 25kHz and 50kHz. Please validate it on your own, since I do not have resources to validate design for our customers.

Best,

Raymond

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TL072: 90 degree phase shifter