Hey
I have a circuit that work with frequency range of 25KHz - 50KHz.
I have op-amp and another devices in the circuit that need to work with VDD and VDD/2 and in some cases I integrate directly into the circuit.
I want to use RF choke to supply DC to the circuit and to block the frequencies.
For this case I search inductor that greater then 1mH but my problem is that all the inductor that I find, there DCR is high.
I work with 3.3V Supply and my max Current is 0.7A so on the Inductor the voltage drop will be very high.
I look about common mode choke with this inductance but their DCR is low, the problem is that I don't have some experience with common mode choke.
My question is if I can use common mode choke like a RF choke? How I can connect it in my circuit.
and another question if there is another solution to replace the RF choke with something else.
Thank you very much

 

How much attenuation does Your project require ?
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want to use RF choke to supply DC to the circuit and to block the frequencies.

What frequencies?

 

What frequencies?

25KHz-50KHz

 

How much attenuation does Your project require ?
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.
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I didn't understand the question. I have a reciever path.
I recieve some signal into op amp and then to adc.
my problem is with the rf choke with the supply voltage and to supply vdd/2 to work with the op amp with single-supply

 

I didn't understand the question. I have a reciever path.

It is time for a schematic. We are all not understanding.

 

It is time for a schematic. We are all not understanding.

I have something like this in my circuit, non inverting op amp with single supply.
I want to put inductor in series to power supply because I want to block my ac signal go through my power supply.

 

I have something like this in my circuit, non inverting op amp with single supply.
I want to put inductor in series to power supply because I want to block my ac signal go through my power supply.

What problem is that causing you?

 

Do the math and it will be revealed to you that an impractical inductance will be required at those frequencies. Do you know what size antenna would be required to radiate any significant energy at those frequencies? You seem to be worried about trifles.

 

Do the math and it will be revealed to you that an impractical inductance will be required at those frequencies. Do you know what size antenna would be required to radiate any significant energy at those frequencies? You seem to be worried about trifles.

I didn't need antenna

 

What problem is that causing you?

I have also some op-amp that want to supply. The total current is 0.7A so the dropout about the inductor will be very high

 

I have also some op-amp that want to supply. The total current is 0.7A so the dropout about the inductor will be very high

That's a lot of op-amps. Most use about 1mA, so about seven hundered?

 

so the dropout about the inductor will be very high

So you are guessing it will cause a problem, as I surmised.

 

I have also some op-amp that want to supply. The total current is 0.7A so the dropout about the inductor will be very high

So you are guessing it will cause a problem, as I surmised.

 

I didn't need antenna

That was my point. You don't have a suitable antenna for that frequency range so radiating RF is going to be the least of your problems.

 

If I was trying to keep RF from getting into the op-amp I would do this.
Add a CLC filter to the supply.
Also add a cap from (-) to (out) of the amplifier to slow it down. It looks like an audio amplifier that does not need to work above 20khz.

The next circuit looks to be a RF power amplifier. Which is not much more than a transistor. Read the data sheet. Give us a part number.

 

If I was trying to keep RF from getting into the op-amp I would do this.

Where did you that idea? As I understand it, he is worried about the 25-50 KHz signal getting, through the power feed, into other devices connected to the same supply.

 

I want to use RF choke to supply DC to the circuit and to block the frequencies.
For this case I search inductor that greater then 1mH but my problem is that all the inductor that I find, there DCR is high.
I work with 3.3V Supply and my max Current is 0.7A so on the Inductor the voltage drop will be very high.

Hi,
where the value of 1 mH come from?

 

I work with 3.3V Supply

That’s not going to work with a TL081 (Minimum supply voltage 4.5V)

 

Where did you that idea? As I understand it, he is worried about the 25-50 KHz signal getting, through the power feed, into other devices connected to the same supply.

yes
This is my problem