OPA549 works in class B? or AB? - diyAudio
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Old 22nd December 2012, 04:45 PM   #1
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Default OPA549 works in class B? or AB?

is opa549 working in class B? i sometimes suspect as its application is more towards servo motors...
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Old 22nd December 2012, 04:58 PM   #2
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Going by what little I could find, I think it has no bias at all on output transistors. I have made a few amps like that using discrete parts driven by an op amp and the results are bad. Harsh sound, and some crossover distortion.
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Old 22nd December 2012, 05:18 PM   #3
Bone is offline Bone  United Kingdom
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According to the data sheet, THD + noise, @1KHz with 25w into 4 ohms is 0.015% with a gain of 3. Quiescent current is between 26 & 35mA. So that doesn't appear to be Class B.
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Old 22nd December 2012, 05:37 PM   #4
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then can it be considered to be class AB?
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Old 22nd December 2012, 07:55 PM   #5
JMFahey is offline JMFahey  Argentina
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I'm quite certain it works in class AB.
A "regular" Op Amp has 2 or 3 mA idle current; this one has 26 to 35mA specified, well into what a discrete, class AB amp of similar power would use.
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