Bridge tied load amplifier

[romaprince]

It's the first time i have posted in this forum cos i'm a new member.

I have a project of designing an amplifier using Bridge tied load model in order to make one which produce 500 W in a 8 -ohm speaker.

Unluckily, i don't have any background knowledge about BTL.

Does anyone have a sample schematic or any guides through which i could use to complete my desired design.


Please forgive me if i have posted in a wrong place.

[SpittinLLama]

You cannot get to 500W into an 8 ohm load with any configuration of chip amps. I suggest starting smaller, a single chip amp kit. Then if you want higher power you can go for something in solid state forum.

-SL

[djk]

To further confuse the issue, how to run a LM3886 off ±100V and get 1KW at 2 ohms (see fig. 11)

http://www.national.com/an/AN/AN-446.pdf

This is called suspended supply operation. To drive 1KW at 2 ohms you would need ten LM3886 in parallel for A1, three pair of MJ21193/94 for Q1 and Q3, one pair of MJE15030/31 for Q2 and Q4, 35V zeners for D3 and D4.

This is a very advanced project and requires 0.1% resistors to set the gain around A1.

[gootee]

Hi romaprince,

A bridged load is driven by two amplifiers, with the "extra" amplifier driving the other side of the load, with an inverted copy of the signal.

Here is a national.com application note covering the basics of bridging and paralleling chipamps, just to familiarize you with the concepts and calculations involved:

http://www.national.com/an/AN/AN-1192.pdf

And below is a national.com appnote with basic examples related to adding power-booster amplifiers inside the feedback loops of opamps. Perhaps you could design something along the same lines as one of the examples (but with a higher-power discrete transistor booster stage), that might meet your requirements, when bridged. (Similarly, look at what djk suggested.)

http://www.national.com/an/AN/AN-272.pdf

However, it would probably be easier and maybe better to use something like the LME49810 with a discrete transistor power output stage. You should be able to get 500W into 8 Ohms even without bridging. See the application information near the end of the datasheet, at:

http://www.national.com/ds.cgi/LM/LME49810.pdf

The datasheet and application notes for the LM4702 will probably also be of interest:

http://www.national.com/ds.cgi/LM/LM4702.pdf
http://www.national.com/an/AN/AN-1490.pdf
http://www.national.com/an/AN/AN-1645.pdf

You might also find some useful ideas in AN18, at http://www.linear.com .

And you might also find some useful devices, datasheets, and application notes, at http://www.apexmicrotech.com .

[gootee]

Are you still here, romaprince?

Below is the URL of another application note, called "Optimizing Audio Bridged Tied Load Amplifiers", from Maxim, that might be useful for you. You can probably use their "optimal" topology and simply substitute your power amplifiers where they have opamps.

http://pdfserv.maxim-ic.com/en/an/AN1122.pdf

[djk]

A very simple high power amplifier design, less complex than the LME49810:

~700w ampifier