Masterpiece

[Stefanoo]

Originally Posted by Joachim Gerhard

When i think more about it maybe there is simply too little current in the input stage.

I have 40mA running on the input stage with 6 BFs each side.

[Stefanoo]

Acting on the input current acts on the gain.
With 6 BFs 3.3ohm degeneration and 60mA LTP I get 63dB.
63mA per side is a huge amount of current. hmmm!!!

anyhow increase of input current and sqeezing everything to the max, it looks like there is not so much gain avaialbe anyway.

[Joachim Gerhard]

For high Gm you need a lot of current that flows in the Fets. A bipolar has 10x higher Gm for the same current so with bipolars you have a much better relationship of idle to Gm.
That is unavoidable.

[Stefanoo]

Originally Posted by Joachim Gerhard

For high Gm you need a lot of current that flows in the Fets. A bipolar has 10x higher Gm for the same current so with bipolars you have a much better relationship of idle to Gm.
That is unavoidable.

true consideration.

Then can this be re-arranged for BJT?
It is a thought I am considering now since the many disadvantages I am encountering with FET, i.e. : of low gm, problem driving a lo Z source, avaialability.

What is your thought on this?

[Joachim Gerhard]

Sure, you can use a bipolar long tail pair but then you have the issue of input DC.

[Stefanoo]

Originally Posted by Joachim Gerhard

Sure, you can use a bipolar long tail pair but then you have the issue of input DC.

DC offset seems to be a minor ptoblem compared to the others. I don't know what you think.
I am trying to re-arrange it but I can't make it properly operate.

[Joachim Gerhard]

This has to be rearranged to balanced but it shows the principle.

[Joachim Gerhard]

.....

[Stefanoo]

Originally Posted by Joachim Gerhard

This has to be rearranged to balanced but it shows the principle.

Is it a scan of the linear audio issue you have recommend? I didn't have time to order it I will do it today and get over with.

I would like to know your opinion if for this balance desing you think we should persue the scheme in rev 7 and try the InterFet device or re-arrange for a differential BJT kind of technology.

[Joachim Gerhard]

I am eager to see the Interfet at work, bipolar works anyway. That is always an option and i did it in the Paradise.
See an even better bipolar low noise circuit. Forget the post before.