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Old 30th July 2002, 02:46 PM   #1
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Default Radical new voltage feedback op-amps

Just a quick heads up on new semiconductor development -- this time from TI.

A new process allows construction of native n-type as well as p-type devices on the same CMOS substrate. Previously, one has depended on "contortionism" to solve this problem. This means several things, both in terms of better analog chips and also for mixed mode devices.

In Q3 2002, TI will have completed their THS4271/4275 devices which are voltage feedback single op-amps. Specifications include high speed (1.4GHz, 970uV/s), low input voltage noise (2,8nV), fast settling (6.2nS to .1%), 90mA drive, low distortion (-90dBc at 30MHz which is low enough not to worry about but not radical)

AND most importantly support for 15V rails unlike some other fast/high performers from Analog Devices.

Looks nice. Now I am really wondering what they are going to do with this process and DAC chips ...

Petter
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Old 30th July 2002, 07:05 PM   #2
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I just read the spec sheet. The supply voltage is 15V total, not +/-15V, so dual supply is +/-7.5V, not enough for audio purposes. Too bad.
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Old 30th July 2002, 08:17 PM   #3
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Default Radical new etc

Morsel,

Why not useable for audio? Your DAC uses a single 5V for audio, that works, doesn't it?
You can probably blow your speakers with 1 or 2 volts into the power amp, right?
Try to think out of the box!



Jan Didden
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Old 30th July 2002, 08:24 PM   #4
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Default Voltage

As a matter of fact, according to the short specs, data is specified for +/-5v.

So I don't see what might be the problem for audio.



Carlos
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Old 30th July 2002, 11:12 PM   #5
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Most audio equipment uses plus and minus 12 to 15 Volt rails. I was replying in the context of Petter's post. It won't be useful for CD player upgrades or headphone amps.
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Old 31st July 2002, 12:53 AM   #6
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I took another look at the specs which say, and found a note stating it was max 16.5V rail to rail so Morsel is right as usual I had originally looked at the 16.5V value defined as VS + checked the drawings which indicated +VS and -VS. My fault, and sad really that this was not an audio rail capability op-amp.

Check out the specs for yourself at http://focus.ti.com/docs/prod/produc...Number=THS4271

Petter
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Old 31st July 2002, 05:19 PM   #7
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Default Wait a minute!

I took another look at the specs. Except for the voltage rating which means I would try at +-9V, perhaps even slightly higher, I think it might still be a winner for selected applications. Compared to the OPA627 audio amp which is supposed to be pretty good this amp has:

Settling time: 88 times better (need to evaluate measurement method as data sheet not complete)

Bandwidth: 26 times better (estimated)

Slew rate: 20 times better (pretty sure this is correctly compared)

Input voltage noise: twice as good

Sounds tempting -- did I hear anyone utter the word active filter?

Petter
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Old 31st July 2002, 11:23 PM   #8
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It will probably self destruct if you exceed the maximum ratings. The AD8610 is a wonderful sounding opamp but several people have fried them within a few minutes on +/-15V rails. They are fine for +/-12V rails. Unfortunately, many of the new otherwise sweet opamps are really touchy about voltage.
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Old 1st August 2002, 12:45 AM   #9
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Hey man, it is the trend of the future. Get used to it. Put a regulator on it, son, youl'll enjoy better.

"Couldn't enjoy it anymore than this."

Ren
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