LME49830 PCB design

[Spasticteapot]

Any news on this PCB?

[berni8k]

Well actually no because i decided to go D-Class.

I have decided to use the TAS5630 from Texas Instruments, its a 600W D-class amp ic inside a tiny SSOP44 chip and runs off a single 20-50V supply.(I have done lots of tiny SMD soldering and board etching so its no problem.)

What convinced me in to that is its simplicity. All the chip needs is a few caps and resistors around it along with a small inductor on each output. It has everything in it, form a input buffer( takes differential too) to the modulator and the power output stage. In BTL mode it outputs two 300W channels and THD stays under 0,05% over half the way there.

Oh and i don't plan on actually using the 600W per chip (Would be a "little" too loud) But i like having the extra headroom also at low powers (For this amp 50W per channel is still low power) the chips should stay piratically cold.

If you people are interested in a homemade 600W D-class i can post up the PCB drawing and updates about it.

[Spasticteapot]

Very interesting indeed.

I'm curious, though - how is the distortion at very low output levels? From what I understand, this is where class D amps aren't quite so stellar.

[berni8k]

Well this chip was just recently released (TQFP packege is not avalable yet)

In the description of the device Texsas talks about PurePath™ HD technology and the feedback it provides.

PurePath™ HD technology enables traditional AB-Amplifier performance (<0.03% THD) levels while providing the power efficiency of traditional class D amplifiers.

PurePath™ HD Enabled Integrated Feedback Provides:
* Signal Bandwidth up to 80kHz for High Frequency Content From HD Sources
* Ultralow 0.03% THD at 1W into 4
* Flat THD at all Frequencies for Natural Sound
* 80dB PSRR (BTL, No Input Signal)
* >100dB (A weighted) SNR
* Click and Pop Free Startup

So yeah from this it almost looks like why bother with the hot AB amps.This is the performance of a AB with near no heating of a D-class along with the simplicity of a chip amp. Only thing is that you need SMD experience to etch a board and solder it. I solder these 0,65mm SMDs without any specialized SMD tools (soldering iron with pointy tip,flux and some solder wick)

[AndrewT]

Hi,
mosfets of the type you have quoted, irfp240, always need bias temperature compensation.
These are Vfets.
They behave in a similar way to BJTs in this respect.

Only the Lfets can be used with a resistor type bias voltage generator.
Lfets are usually expensive and most builders avoid simply because of the cost.