is it possible to bias opa627 into class A? - diyAudio
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Old 23rd November 2012, 03:59 PM   #1
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Default is it possible to bias opa627 into class A?

i have a pair of opa627 very impressed with its highfreq performance and would like to make this chip work in class A.. is it possible did somebody do this before how about stability and performance and heat issues...
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Old 23rd November 2012, 04:13 PM   #2
jcx is offline jcx  United States
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Class A depends on load - for driving a 50 kOhm volume pot most op amp outputs factory internal bias already is Class A

so you really have to know the signal, load - and the limits of the op amp - many may additionally distort from current drain that is even a modest fraction of their rated output

careful meausurement of actual op amp with load is needed to see if, or by how much you are improving distortion - often a 2x THD reduction is all that is found

2 op amps can be paralleled, biased "against each other" in push-pull, of course with significant Class A current bias you have to deal with the heat:

Opamp based Amps - Question

I like multiloop composite circuits - use the OPA627 as the input and global feedback stage around a 2nd op amp with much higher current specs - easiest to compensate with a really fast output op amp - like a CFA - TPA6120/THS6012 is great for line driving, most dynamic headphones:

High loop Gain Composite Op Amp Circuits

Last edited by jcx; 23rd November 2012 at 04:29 PM.
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