To simulate such a circuit, you need to be extremely careful in selecting the value of the current source. We fiddled it to the 6th significant figure, and got the sim to work without problems. But the sim does not tell you the real problems, which is the different tempco between PMOS and NJfet.
If you mean by mass produce = <1000 pcs GB, then it can be arranged. BUT you still have the thermal drift issue, and someone need to match the FETs. If you mean by custom made IC, it is also possible if you are prepared to pay for the set up charge, etc. I think you need to be prepared to make >>10k to get the price to a reasonable level. AND then you can trim DC offset by laser. But then who can make a NJFet plus a PMOS or PJFet ? None of the foundries. And I doubt you can get NXP to be excited about this unless you put a 7-figure sum on the table.
A degenerated PJFet will also help to reduce noise and increase stability, at the price of open loop gain.
Patrick
If you mean by mass produce = <1000 pcs GB, then it can be arranged. BUT you still have the thermal drift issue, and someone need to match the FETs. If you mean by custom made IC, it is also possible if you are prepared to pay for the set up charge, etc. I think you need to be prepared to make >>10k to get the price to a reasonable level. AND then you can trim DC offset by laser. But then who can make a NJFet plus a PMOS or PJFet ? None of the foundries. And I doubt you can get NXP to be excited about this unless you put a 7-figure sum on the table.
A degenerated PJFet will also help to reduce noise and increase stability, at the price of open loop gain.
Patrick
I've finally had a good chance to come back and play with the circuit.
Well actually I have to go back even further and play with the circuit in the Diy op-article.
Definitely very touchy to simulate. But I've gotten something that actually has the output I would expect.
It'll take me a while to go from sim to the real world, but I'd like to say thanks for a bit of inspiration.
Or perhaps you just want to advertise for your GB ?Patrick
I think so.
the first PCB I had made was this:
An externally hosted image should be here but it was not working when we last tested it.
Not my design, but a little larger than the DIP-8. Open loop buffer designed by Sijosae, made to fit onto a DIP8. The layout was by "mono" at Head-Fi
Distortion isn't everything, you know.
Besides, the 0.3ppm THD plus noise figure of the LM4562 doesn't imply that the preamp you'll build with that opamp will match it's number, you'll have to grab hold of your socks to accomplish olympic digits.
For what it's worth, the preamp i have still holds the globe's no1 position in low thd+n for all-discrete designs.
An excellent LM4562 build is the RelaiXed design by cheeso Jos van Eijndhoven, sounds absolutely great for a full opamp pre, also balanced in/out for a happy meal ticket.
The full discrete beats both the distortion figure and sounds better, for a logarithmic scale price tag and significantly more idle dissipation than a blowtorch.
The 18mA bias level of the discrete dip8 also makes it more versatile than the LM4562, Class A is what this part of the forum is about.
Besides, the 0.3ppm THD plus noise figure of the LM4562 doesn't imply that the preamp you'll build with that opamp will match it's number, you'll have to grab hold of your socks to accomplish olympic digits.
For what it's worth, the preamp i have still holds the globe's no1 position in low thd+n for all-discrete designs.
An excellent LM4562 build is the RelaiXed design by cheeso Jos van Eijndhoven, sounds absolutely great for a full opamp pre, also balanced in/out for a happy meal ticket.
The full discrete beats both the distortion figure and sounds better, for a logarithmic scale price tag and significantly more idle dissipation than a blowtorch.
The 18mA bias level of the discrete dip8 also makes it more versatile than the LM4562, Class A is what this part of the forum is about.
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...but NJR made several high Ic opamps
Who is NJR ?? I have never heard before. Let me know types and URL's about this (or mean you the NJM series from Japan Radio Company ?) - thank you.
An other question: who have heard the sound character of the discrete OP-AMp solution from here against the IC types LME49710/4562 (e. g. in a line or RIAA part from a preamp)?
http://www.diyaudio.com/forums/soli...me49720-lm4562-lm-4562-lme-49710-49720-a.html
Thank you for your comments about your impressions
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