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Old 6th December 2012, 04:57 PM   #7951
MiiB is offline MiiB  Denmark
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Reason I threw the one-shot in the pool was the LPT balancing option, I brought it forward as a topology to use the those high GM-fets you were sourcing.. The one shot is however an interesting topology, and used right it may hold surprising results.
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Old 6th December 2012, 05:42 PM   #7952
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I have some IRF P-Mos i can try, maybe tonight. Yes, P-Mos are much more quiet then N-Mos. I also thought that there could be a way to make a gyrator with lateral enhancement
P- channel MosFets.
I know one that could work.
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Old 6th December 2012, 05:50 PM   #7953
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And here is a very good idea for a temp compensated CCS.
Similar to my idea but this is purely CCS.

It looks like it could work very well indeed.

Do we want to formalize this idea or you don't think it could work out?
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Old 6th December 2012, 05:53 PM   #7954
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Quote:
Originally Posted by Joachim Gerhard View Post
I have some IRF P-Mos i can try, maybe tonight. Yes, P-Mos are much more quiet then N-Mos. I also thought that there could be a way to make a gyrator with lateral enhancement
P- channel MosFets.
I know one that could work.
What do you mean? Trying IRF9610 to see how it works temp wise or were you referring to some other IRF?

The idea of making a gyrator with laterl mos seems pretty interesting.
What is your idea all about?

Consideration aside that might be worthwhile: making a temp compensated CCS the way re-ported on my previous post using a steep P-MOS could actually be a good idea.
The benefit would be that the differenctial amp would have to swing less to correct also they system would work on a tiny portion of the transcharacteristic thus taking full advantage of linearity that could also improve.
Does it seem fair?
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Old 6th December 2012, 06:04 PM   #7955
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Stefano, that is an enhanced CCS with opamp, could work. Yes, i will try IRFP9610.
The lateral mosfet i am thinking about comes in a bigger case. As Frans and i have discussed, the bigger the better. 50mA is a decent current to get good Gm out of the lateral. The biasing then runs on lower voltage because laterals need less Ugs.
Also laterals do not have that sharp current over voltage curve that other mosfets have.
Another option is to raise the gain in the cascode. That is possible with the so called " Gain Boosted Cascode". It was invented for mosfet integrated circuits where space is limited. Here you can find such a circuit :The Designer's Guide Community Forum - Gain-boosting cascode_zeros
When you google you can find more. It should also work with a J-Fet BJT cascode.
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Old 6th December 2012, 06:18 PM   #7956
FdW is offline FdW  Netherlands
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There is some info here Mosfet Gyrator using the IRF840
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Old 6th December 2012, 06:19 PM   #7957
FdW is offline FdW  Netherlands
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And also here Cascoded MOSFET Gyrator | Bartola Valves
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Old 6th December 2012, 06:23 PM   #7958
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Lateral approach sounds interesting.

Just to show my complete lack of knowledge and great ignorance in electronic to all people here who have been kindly pointed that out for me and thank you for that....here is a very simple circuit I drew in a couple of minutes and I think has the potential to be integrated with the design.
If it works, it will ensure low noise and high gain and I already have RIAA values ready to a great RIAA precision with this design.

Anyway setting jokes aside.......let me know what you think.
You might want to try this with IRF9610 and if you are interested I can share RIAA values with you and if you have the set up you can start making bench consideration.
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File Type: jpg CCSJPG.JPG (79.7 KB, 126 views)
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Old 6th December 2012, 06:23 PM   #7959
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Quote:
Originally Posted by Stefanoo View Post
And here is a very good idea for a temp compensated CCS.
Similar to my idea but this is purely CCS.

It looks like it could work very well indeed.

Do we want to formalize this idea or you don't think it could work out?
FYI this is Fig. 2 of US patent 5389889 by Towne et al., Allegro Microsystems Inc.

Temperature-compensated current source for use in a hall analog magnetic-field detector - Allegro Microsystems, Inc.
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Old 6th December 2012, 06:24 PM   #7960
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Actually with the lateral i am thinking off it is a bit tight. For 50mA they need only 0,25V.
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File Type: png 0.25V 50mA.png (89.9 KB, 133 views)
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