Part Number: TPA3128D2
Other Parts Discussed in Thread: LM4766
I have a personal project (marketable product) for which I could use up to 6 channels of class D amplifiers, but I have been waiting and waiting for something of an open architecture to come around, and so far it is not happening. I need something like the class AB LM4766, that I can use EXTERNAL feedback, but in class D. I don't know why this seems to be so hard to find. All class D devices I see, from TI or from others, all of them have internal feedback.
Note that this is NOT in order to set gain. I know that there are some devices that integrate a gain control. That's not what I'm after; I'm after being able to include more than just output voltage in the feedback path. I have other signals I need to integrate, such as a function of output current into the feedback signal. I have already proven the concept using class AB audio amplifiers, and can't reveal more details in a public forum; but, what it boils down to is that I need a device that can be used as if it were a power op-amp, accepting --and requiring-- external feedback, but operating in class D. I have no problem with that there be design considerations regarding limiting the feedback's bandwidth and/or gain constraints, but I cannot make do with the typical class D black-box chip already having feedback networks built-into it.
Any prospects for such a thing?
P.S.:
And yes, I have considered using an opamp based pre-amp circuit to implement my feedbacks to, bypassing the class D stage; but doing that would put two amplifier stages into the feedback path... Not too nice, though if I use a video BW op-amp for the pre stage, the fact of having a 2-stage feedback is probably a non-issue, I suppose. If worse comes to worse I will try that, but would rather not do that, if possible.
