Return-to-zero shift register FIRDAC

[ThorstenL]

True. But there are still minor hysteresis loops around the selected operating point?

Yes, the core is never perfectly linear, just like transformers. So some form of zero field operation is desirable.

Like zero ohm source, infinite load or Infinite impedance source and zero ohm load.

In my case I used low source impedance and relatively high load impedance. And Bias and "chonky" inductors.

See here for more on distortion and inductors...

Thor

 

[Hans Polak]

By applying DC current bias we move to one of the sides of the hystresos loop and never "cross zero".

That seems to be based on a misunderstanding The farther you move from the zero crossing, the stronger the hysteresis.

Hans

 

[ThorstenL]

Hans Polak
That seems to be based on a misunderstanding The farther you move from the zero crossing, the stronger the hysteresis.

I should have stated hysteresis distortion...

The greater the DC bias the smaller the minor loop, as area between the two curves narrows.

Thor

PS, Hans please note I have you on ignore, so if you reply and do not get reply back it is because I normally do not see your responses.

 

[ThorstenL]

We are talking about harmonic pumping, but it's not just about harmonics...
I did a test for low levels of the carrier frequency

But I think that's we see it only. This is not real pumping.
It rather results from the way of the measurements.

This is very possible. Measurement artifacts.

BTW, I stumbled across this. Not sure if it is of any value to those who do their own modulators, like Pjotr and Marcel, so I'll just drop it in here, as we do discuss these in passing.

Audio Engineering Society Convention Paper - Simple, Ultralow-Distortion Digital Pulse Width Modulator

Thor

 

[MarcelvdG]

I should have stated hysteresis distortion...

View attachment 1320118

The greater the DC bias the smaller the minor loop, as area between the two curves narrows.

Thor

In your second picture, the core is driven halfway to saturation. (The associated inductance loss will actually still be small in a core with an airgap.) I didn't realize you were referring to DC currents large enough to do that. For power inductors, it may take amperes rather than a milliamp or two.

 

[Markw4]

Regarding modulators, there is some more recent work of possible interest, but too large to attach here.
https://www.dropbox.com/scl/fo/mb53...C3bfbYhQ?rlkey=15v1k5o04r9j0bkd92ifhrfpp&dl=0

 

[ThorstenL]

In your second picture, the core is driven halfway to saturation. (The associated inductance loss will actually still be small in a core with an airgap.) I didn't realize you were referring to DC currents large enough to do that.

Even a smaller current shifts the minor loop. It's all a question how much and what inductor is in use, which in turn depends on circuit impedance's.

My application was an 80kHz RCLC filter terminated into 10kOhm.

Thor

 

[ThorstenL]

I mentioned interleaving RTZ DAC's before and I think we never got on the same page.

I finally located the Patent I had found before:

Dual return-to-zero pulse encoding in a DAC output stage

This may clear up any misunderstanding we had before regarding this.

Thor