Discrete I-V converter

[syn08]

Smart people may occasionally generate stupid ideas (and post #10 is a good example) but then they don't deserve being called stupid. However, stupid people will rarely generate a brilliant idea and then they don't deserve being called smart for.

 

[Terry Demol]

With an input resistance of 1Ω, the resistance of the source is irrelevant whether it is 1K or infinity.

That is not always the case. With a true high impedance CCS type DAC OP impedance, the I-V will usually measure its lowest distortion. Lowering OP Z of
DAC will usually increase the distortion of I-V.

TCD

 

[Rumen]

Do not blame Sandy for his manner of expression! He also call us /bulgarians/ stupid in our forums. Especially audiophile ones. He is just that type of man. Аlways says what he thinks.
Buuut, he knows everything about electronics.

 

[jean-paul]

Otherwise, we're just more honest and tell the truth. When someone writes nonsense, we tell them so.

Well it depends what is seen as the truth but I think that nails it. I have no problem with it at all but the west seems to become oversensitive to words. This even more so with the ridiculous phenomenon "woke" that expands like an oil stain.

 

[Hans Polak]

That is not always the case. With a true high impedance CCS type DAC OP impedance, the I-V will usually measure its lowest distortion. Lowering OP Z of
DAC will usually increase the distortion of I-V.

TCD

Hi Terry,
What exactly do you mean with influencing the OP Z of a Dac ?

Hans

 

[Hans Polak]

Well it depends what is seen as the truth but I think that nails it. I have no problem with it at all but the west seems to become oversensitive to words. This even more so with the ridiculous phenomenon "woke" that expands like an oil stain.

I’m afraid that you are confusing the careful selection of words with social awareness issues, two worlds having nothing to do with each other.
Being rude and aggresive seldom promotes a lively and constructive discussion.

Hans

 

[jean-paul]

No I don't think I confuse anything in my reply in post #24 to SandyTodorov1's remarks in post #18. The subject was definitely not "rude and aggressive" (which you try to make it and of which you would be right) so it seems you are confused. Besides that the opposite of what you state would be equally counterproductive. Sorry.

 

[lcsaszar]

Just a small remark: the OP always can edit his post including the topic title. This also belongs to respect to others.

 

[jean-paul]

Really? I think the content can be edited and not the title?! At least that is what it used to be.

Should be "Discrete I-V converter" I think.

edit: I just tested and I can still edit content of old threads started by me but not the thread title as already mentioned.

 

[bimo]

Why on earth should someone be jalous.
What a strange hypothesis for a non commercial DIY forum.

Hans

Jealous can happen every where. Jealous that other person smarter or richer or more success or more beautiful, etc.

In this context is about very low THD I/V converter. I did the simulation and I can confirm it is very low THD. I understand how it worked. The question is the implementation. What about the measurement?

If you do not understand how it worked you can ask. If you do not believe it can be implemented, than you can ask the measurement.

 

[lcsaszar]

Really? I think the content can be edited and not the title?! At least that is what it used to be.

Should be "Discrete I-V converter" I think.

edit: I just tested and I can still edit content of old threads started by me but not the thread title as already mentioned.

Sorry then, my mistake. Still, the mod can do it.

 

[jean-paul]

If the OP reports his own post so I suggested this by PM.

 

[AllenB]

Can I be of assistance?

"Discrete I-V converter"?

 

[jean-paul]

It is already changed I see so thanks

 

[Hans Polak]

For PCM1794

With all respect, but what exactly would be the reason to build a very complex discrete I-V converter these days.
With modern opamps as in the image below, one can achieve simulation figures of resp. 2ppm%@1Khz, 10ppm%@10Khz and 137ppm%@100Khz for +/2mA in and +/8V out while just producing ca. 3uV noise from 20Hz to 20Khz.
For the 1794 gain should be halved since it produces +/-4mA, the above figure were to make them comparable to yours.

Hans
.

 

[bimo]

With all respect, but what exactly would be the reason to build a very complex discrete I-V converter these days.
With modern opamps as in the image below, one can achieve simulation figures of resp. 2ppm%@1Khz, 10ppm%@10Khz and 137ppm%@100Khz for +/2mA in and +/8V out while just producing ca. 3uV noise from 20Hz to 20Khz.
For the 1794 gain should be halved since it produces +/-4mA, the above figure were to make them comparable to yours.

Hans
.

My version show 0.000015% at 20kHz 4V peak in simulation (buffer output), just saying...

Some people make discrete op-amp although it is not better than the best op-amp. Syn08 built amplifier with THD 1ppm at 20kHz. Wenzel design an amplifier with 10MHZ full power bandwidth and Jan Didden built it also.

It is DIY. Did you see the joy to make a design? Simple one, complex one, mediocore one, superior one, etc.... It is fun.

 

[sesebe]

those values of distortion are only reached in a simulation with identical values of each transistor pair. Maybe a monte-carlo analysis should be done even when it takes a long time to simulate.

You also have to have a proper model of your DAC working into your input impedance, that is where most problems will arise.
I think 2 good opamps and a modern differential output DAC will give you much better results.

I'm totally agree with this!

More interesting will be to see measurements that confirm the statement that the people that still use op-amps are stupid.

 

[donovas]

Very nice circuit, hans.

I assume the 2nd stage is a buffer?

If so id like to use it as a zero gain preamp if possible

 

[Hans Polak]

The main function for the OPA1632 is to levelshift the signal to zero volt and to produce a true differential output signal with one single amp from both input signals.
For a PCM1792/1794 as an example the bias from the Dac is -6mA giving a permanent 6Volt output bias from the first opamps that has to be level shifted.

Hans

 

[dreamth]

Just another eastern european opinion on the good old days of easy peasy audio : achieved by Technics in the 90's...40...50db less distortions for odd harmonics and nice monotonic decrease of even harmonics:
https://www.diyaudio.com/forums/ana...amuel-groners-super-opamp-18.html#post5810841
https://www.diyaudio.com/forums/ana...amuel-groners-super-opamp-15.html#post5797767