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80 lines
2.3 KiB
80 lines
2.3 KiB
on the patent
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its the Vbe TC that is used.
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on the lm334,
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it's the IC, and an external diode for the TC equalizing (if you use the example circuit later on to
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balance the TC)
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on the patent
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figure 3 is the basic example.
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fig 1 omits the current mirror.
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figure 3 is described in the details section of the patent
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figure 4 or 5 has additional balancing.
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todo: build figure 20, and test to see what kind of current lowering I can get
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todo: build transistor only circuit of this current source, based on schematic in LM334 data sheet.
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might need multiple emitter transistor EDIT: I don't think so. they aren't common in standalone packages.
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only on ic die. and some are not true multi emitter, but just two bonded leads to the same emitter.
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https://en.m.wikipedia.org/wiki/Multiple-emitter_transistor
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article in edn covers what bob pease has for a circuit. similar to ti data sheet with transistor, but drives
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constant current for an led
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current source notes: 09/20/20
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st and ti schematic are slightly different, extra base connection on st.
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lt schematic is different from those. it adds two mosfets.
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as per ken sherrif blog, theres no such thing as a standard part
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in electronics, so likely every manufacturer implements the
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lm134 differently. Decapping would be useful here...
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There is also a concern that ICs allow for different techniques than discrete (but I bet a discrete LM134/334 is still
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possible).
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issue is that second row of transistors is not activating (the npns)
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Further research needed:
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check discrete lm741 by evilmadscientist labs and evaluate how they adopted the op amp from its schematic to discrete
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components:
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https://shop.evilmadscientist.com/productsmenu/762
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as discussed here:
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https://www.eevblog.com/forum/beginners/555-from-transistors/msg1451815/#msg1451815
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and
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https://www.eevblog.com/forum/beginners/how-hard-is-it-a-make-a-transistor-opamp-like-lm358-chances-of-working/msg1403648/#msg1403648
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Perhaps in the meantime, I could make just an op amp current limit circuit based on
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the diagram in the LT data sheet notes (Page 5, basic theory of operation). Decapping and reverse engineering of a few LM334 would be useful.
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if I had $450 I could buy a wafer...
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https://www.digikey.com/products/en/integrated-circuits-ics/pmic-current-regulation-management/734
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hah
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