ok maybe this is a stupid question or maybe not
ive always wondered why each chip has to have its own parts and why you cant just put one chip on top of the other(connect the inverting input to the other chips inverting input etc instead of having to use 2X as many resistors etc. if anybody has an answer to this please let me know as im very curious. i have never tried this before as in i have no speakers i am willing to blow to test this. but if anybody tried it let me know the results.
thanks.
ive always wondered why each chip has to have its own parts and why you cant just put one chip on top of the other(connect the inverting input to the other chips inverting input etc instead of having to use 2X as many resistors etc. if anybody has an answer to this please let me know as im very curious. i have never tried this before as in i have no speakers i am willing to blow to test this. but if anybody tried it let me know the results.
thanks.
Holy chip, it works! I tried it with two LM3875,S I had laying around. Split the input with 2 1K resistors and 1 22K to ground used a common feed back loop with a 22.1K .1%, 47uf tantalum cap, and a 1k .1% to ground fed the outputs to two .15 ohm 1% soldered directly two the pins and took the feedback of the combination of outputs. Might have to take a closer look at this! I got the least amount of DC offset of any chip amp Ive made!!
cap removal
The tantalum should not be removed for DC offset, you also need current resistors, but you can use a common feed back network. I would post pics but my wife is out of town and has the digital camera.
I had this strange idea of potting the hole thing in epoxy and soldering the chip to a piece of copper and basically building a parallel module
The tantalum should not be removed for DC offset, you also need current resistors, but you can use a common feed back network. I would post pics but my wife is out of town and has the digital camera.
I had this strange idea of potting the hole thing in epoxy and soldering the chip to a piece of copper and basically building a parallel module
so let me get this straight you can do it, as long as you have a 47uF in the fb? would that be parallel to the fb resistor or series with it? im a bit confused.
the output .1 ohm resistors i kinda figured they would be used in the first place for current sharing but i do not understand the 47uf in the feedback loop.
the output .1 ohm resistors i kinda figured they would be used in the first place for current sharing but i do not understand the 47uf in the feedback loop.
tiltedhalo said:Holy chip, it works! I tried it with two LM3875,S I had laying around. Split the input with 2 1K resistors and 1 22K to ground used a common feed back loop with a 22.1K .1%, 47uf tantalum cap, and a 1k .1% to ground fed the outputs to two .15 ohm 1% soldered directly two the pins and took the feedback of the combination of outputs. Might have to take a closer look at this! I got the least amount of DC offset of any chip amp Ive made!!
How hot does the chips get? I have a hard time believing it is that simple . I mean why would manufacturer who uses chips in parallel use so many extra parts? I hope you are right and your amp can be duplicated by other.
parallelling chips
In all honesty your only saveing 2 resistors, everything else remains the same. You still need current shareing resistors ect., the only differance is your useing a global instead of local feedback network, this has been used for years with other op amps.
In all honesty your only saveing 2 resistors, everything else remains the same. You still need current shareing resistors ect., the only differance is your useing a global instead of local feedback network, this has been used for years with other op amps.
Ok the tantalum cap can correct the internal dc offset of each chip? Have you measured each chip's offset separatly? It seem to me that if you dont get each chip's offset down before paralleling them,you will still get quite a bit of curent share even if you have resistors at the output.
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