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Old 20th January 2003, 07:13 PM   #1
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Default Anyone ever do anything with the TI opa 548?

It is made by BB/TI, and looks to be pretty decent. Has anyone ever tried to make an amp using this?

-Paul
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Old 20th January 2003, 07:18 PM   #2
joensd is offline joensd  Germany
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Hi Paul,
just received some samples of that kind.
There is a application note for an amplifier called "complete audio amplifier" from Burr Brown (TI). Its with tone control but you can leave that out if you want to.
A lot of people use it for power supplies as well.

Jens
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Old 24th January 2003, 11:11 PM   #3
ppl is offline ppl  United States
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Default Nice Battery Powered 10 Watt Amp

I made a small stereo amp using a pair of OPA-548,s in Bridge mode. with 8 ohm and above Loudspeakers I have used 6 ohm ratt shack LS-5's at one time and it worked but the Hammond 1455 series exturded aluminium case got real warm almost hot. The case also serving as a common heatsink for all (4) OPA-548's. The reproduction is alot better than the Car stereo IC power Amp Chips, althought the Car IC's do power lower impedance loads better.

Topology wise the OPA-548 is more akin to your nomal Op Amp than the Car stereo IC that most often has rail to rail single supply and an all NPN output stage. The OPA-548 on the other hand uses a true differential Input and Complimentry Output Emitter follower output stage both of these i am strongly in favor of and the Complimentry output stage of the OPA-548 is a futher Bonus in Bridged applications where Both the Advantages of an ALL NPN output stage and Complementry symmectrical output stage transistor Pairs all in one.

The attractive aspect of the OPA-548 vs your typical Car stereo IC is First a Bridged stereo amp will have about 80 mA quesent curent and work op to 30 volt supplys. The Car stereo IC stereo Amp will require about 300 mA. The low voltage operation is similar to car stereo IC's with a 7-8 volt min. however, the Max on the 548 is about twice that of a Car IC @ 30 Volts.

In coclusion I am happy with its use as a small light weight High Quality Stereo Amplifier. would also be great in Powered loudspeakers desireing Battery opation.
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Old 4th May 2003, 09:22 PM   #4
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Default ppl

Yes- although this is an old thread, I just posted on the 548 & was encouraged by your info. I had not dissected the internals of TI's product, but I can say with certainty that the 3886T is a quasi-complementary beastie. I have not been impressed W/ the sound, tube like or not. The TI does cost more money, BTW.

I am led to wonder about a car circuit that could produce -(that's minus) 14.2V, which is a running car, +/-. It could be ballasted by a small batt (to say nothing about boomer caps) and the result would be decent at 4 ohms without bridging. These chips could be paralled for reliability, and heat-sinkery.
I realize this puts us into the murky world of mosfet switchers , but can't the folks here come up with just about anything?
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Old 5th May 2003, 11:11 PM   #5
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I know nothing about switching PSUs, but I have made about 14 channels worth of 458, using various inverted versions, and I think it is one of the nicest amps I have ever heard, better than the usual LMs any day

If anyone wants a pcb layout, one I did is here.
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Old 6th May 2003, 07:41 PM   #6
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yes, i made a stereo amp with them before i made my OPA541 amp that i am working on at the moment. they were ok, im no audiophile so i dont have an opinion on sound quality :P
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Old 7th May 2003, 12:47 AM   #7
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One advantage of OPA548 over 3886/3875 is that it is unity-gain stable while the datasheets of 3886/3875 said their voltage gain cannot be less than 10.
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