Single or dual differential?

[ppl]

Ok hears is what i am playing with however severial undocumented revisions have happened since

[lumanauw]

Hi, PPL,

Where's the folded casocode? Connection of Q3-Q4 to Q5-Q6 seems to be double differential? This one has huge OL gain, folded cacode has very low gain

[AndrewT]

Hi Ppl,
I am looking for the folded cascode, but I cannot see it.

Have you posted the correct schematic?

[ppl]

Well if taken from a academic point of view the addition of Q5 and Q6 changed the topology from the folded Cascode to a Jfet/BJT Cascode Input Diff amp cascaded to a BJT Cascode Diff amp loaded by a Current Mirror, however that’s too long of a file name after this design is stable without compensation capacitors I can do a PCB up and its then fit to release to the DIY headphone community the name can then be changed to something totally non technical. Attached is what this project started out as and as you can see it is technically a folded Cascode, it actually works for such a simple circuit but not real stellar THD and noise. After looking real close at the schematic to the OPA627/OPA637 IC monolithic Op-Amp’s on the cover of it’s data sheet I saw the pathway to lots of OLG. http://focus.ti.com/lit/ds/symlink/opa627.pdf

[Elso Kwak]

Originally posted by ppl
...... Attached is what this project started out as and as you can see it is technically a folded Cascode, it actually works for such a simple circuit but not real stellar THD and noise.

Hi ppl,
Actually I had very good results with it sonically. You can improve on the current mirror. Cascode the FETs. See my KISS amp:
http://www.diyaudio.com/forums/showt...432#post507432
You current circuit similar to the OPA627 schematic I started with....

[ppl]

Originally posted by Elso Kwak



Hi ppl,
Actually I had very good results with it sonically. You can improve on the current mirror. Cascode the FETs. See my KISS amp:
http://www.diyaudio.com/forums/showt...432#post507432
You current circuit similar to the OPA627 schematic I started with....

Thanks alot for the KISS amp link I must say you used about every Trick in the Book on the Front end of that. I myself however like to use LED voltage references as you also do, I i remember Right Green is low noise and capacitence. So if i used some of the technique you used in your Kiss Amp in my Now apperently incorrectly named Headphone Amp, this would be ok with you? I really like the second gain stage current mirror. A three transistor mirror. and refering the reference back to. Also like yourself it was the OPA627 that inspired my topology also. Strange how manny different people will be thinking the same thing all at the same time, that is so Cool!

[Elso Kwak]

Hi ppl,
Am I seeing double on 1st Easter day as I see a 5-transistor current mirror?
Of course you can use it. I found it in a book: Electronische Implementatiekunde by Gerard C. M. Meyer, Delftse Universitaire Pers. (page 138). I only replaced the diode-connected transistor by a green LED. You will find it also in ICs where transistors are used at abundance. Old Harris data-books are full of them. It's a cascoded current mirror to counteract the Early effect

Which reference are you referring to?

[lumanauw]

Hi, Elso Kwak,

In the KISS schematic, the differential is CCS'ed by BC550C running at 80? This BC550C works OK with 80V?

[Elso Kwak]

Originally posted by lumanauw
Hi, Elso Kwak,

In the KISS schematic, the differential is CCS'ed by BC550C running at 80? This BC550C works OK with 80V?

Hi lumanauw,
There are some fatal errors in the schematic!
You spotted one of them.

[ppl]

Thanks I will put that into my last version of my Design and see what it sim’s like afterwards. The Three transistors Wilson type current mirror I was referring to are the upper MAT-02 with the BC5460? I did not refer to the lower Cascode part of that Yes 5 transistor Cascode Current mirror. What Harris op amp uses that topology? The reference I was referring to is the Green LED between the bases of the upper and lower Mat-02’s

Oh BTW so has anyone come to a conclusion if a Complementary Differential diff amp stage is an improvement upon these Circuits like in the KISS Amp.

On another note the U440 is a great dual fet I have used them a lot. I don’t like the sound of the Mat series of Duals from ADI, These impart an IC op Amp quality to the sound. The Best sounding Duals both BJT and fet are from these guys http://www.linearsystems.com/ They sell direct and have superb electrical matching. But what attracts me to this company is the sound of there devices, for example the U-440 is available from both LIS and Fairchild yet the LSI part has lower DC offset and like the Fairchild U440 dose not sound like an Op amp, more over is you like the u-44 you will love the Blackness in the background that the LS840 and LS843 give, you do lose some crispness on the top octave with the LS parts over the U440 but micro dynamics to Die for with a properly biased LS-840,LS-843
LSI data sheet U-440 http://www.linearsystems.com/datasheets/U440.pdf
LSI data sheet LS840 http://www.linearsystems.com/datasheets/LS840-2.pdf
LSI data sheet LS843 http://www.linearsystems.com/datasheets/LS843-5.pdf
For Dual Complementary BJT’s I like the LS312 and LS352 better than the ADI parts however if theADI device is all that’s available ill use them.