Discrete Opamp Open Design

[RNMarsh]

Just noting the results and what I will use and why. To each his own. BUT and IF I can buy this thing from a vendor in taiwan with or without smd, I'll try it at least. Making it myself is not the great fun it is for most over here in the DIY category.

That reminds me -- how is the pcb coming along?
Got my Audio Precision brought over and doing some work (as thier ex -CEO) and play.... Got a lot of software to buy while still in S.E.Asia... -RNM

[fas42]

Originally Posted by bear

but, what, no error correction circuitry?

inquiring minds want to know?

_-_-bear

They call that feedback resistors, fiendishly cunning designers ...

But, the intrinsic design has remarkably good distortion figures, performs excellently even at very high gains ...

Frank

[qusp]

Originally Posted by Wavebourn

Vishay today is the common name of the holding that bought many companies, together with their production and techsupport. Hence it's name does not mean high quality.

vishay precision group (VPG) I think you will find is still just the one company. there are simply not that many factories geared up to make this stuff. besides like I said, better to buy from Texas components unless you need very large production quantities

[RNMarsh]

Originally Posted by fas42

They call that feedback resistors, fiendishly cunning designers ...

But, the intrinsic design has remarkably good distortion figures, performs excellently even at very high gains ...

Frank

Got FFT's on a working prototype ??

[qusp]

Originally Posted by RNMarsh

To each his own.

agree totally!

BUT and IF I can buy this thing from a vendor in taiwan with or without smd, I'll try it at least. Making it myself is not the great fun it is for most over here in the DIY category.

me too, but at least at this stage it seems not to be the BF862 version? myself I still love building though, mainly so I can make idiosyncratic parts choices =)

[fas42]

Originally Posted by RNMarsh

Got FFT's on a working prototype ??

Nope, this is purely from sim fiddlings ... I'll be keeping entirely out of the building game, my interest in the exercise at this point is to see how closely sim behaviour can match up with real componentry working, and to investigate whether the sim mechanism can help to refine the design in any areas. Also, I enjoy understanding how circuits tick by looking at the waveforms at various points through the beast ...

One thing that is intriguing, is that the distortion figures hardly vary if different BJTs are used, but the PSRR figures change dramatically ...

Frank

[Wavebourn]

Sure Frank. When Scott knows what to SIM and feels how to tweak, it can help to refine the design.

[RNMarsh]

Warning to No More Deadline Scott..... I am suppossed to be retired... but a company i was CEO for several years had its president die and now I am back here in Bangkok helping with product development. Seems there is only one way out.

My main interest was to have SW (by hook or by crook) to put his immense knowledge and talent for analog design out and up and running for the benefit of all -- before he retires (?) :-)

besides C of high C jFEts and its affect on PSRR - are there any other factors you found to make a big difference in PSRR. That is interesting to me as it gets little attention elsewhere.

BTW - I find the same thing re transistors make a minor difference in an audio designs' THD where the topology dominates and why symmetrical/balanced topologies are so important. Thx - RNM

[fas42]

Originally Posted by Wavebourn

Sure Frank. When Scott knows what to SIM and feels how to tweak, it can help to refine the design.

Tsk, tsk ... everyone has their own approach and ideas on things, I enjoy playing with other people's ideas, to see where that can lead, since I'm coming from a completely different perspective.

For example, I feel the +ve PSRR figure could go a bit better at high frequencies, trying a few things to see what makes a difference, but apart from extra cascodes haven't come with anything significant so far ...

Still a lot to explore; as I've mentioned before I have very little instinct for how such circuits work, so this is a journey of discovery for me ...

Frank

[PHEONIX]

Hello

Thankyou Scott and Barsco for your approach to fet matching.

I have another fet question that you might be able to shed some light on, do you know what the closet fet is that is used to make up the J500 series of Current Regulating Diodes.

Regards
Arthur