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Old 3rd August 2004, 12:07 AM   #1
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Default High power Amp with OPA445

what the parts i need to put in the pic......that it will realy work.

and how mach power is with 35V + -...

thanks....

tamir
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Old 3rd August 2004, 11:57 PM   #2
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what worng?!
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Old 5th August 2004, 12:26 AM   #3
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Looking at the picture, I guess that the op-amp has a VAS stage as the output from it, and then drives a 'similar to' darlington output EF stage. The drivers appear to be biased by a current source, I think this could work.
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Old 5th August 2004, 08:52 PM   #4
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it is need to work !! it is have to be...!! it is from the compeny of the opaamp.

but my Q is.... what kinds of transistors i need to connect to get him work....

and how much power that is?

thanks
tamir
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Old 5th August 2004, 11:09 PM   #5
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Q3 & Q4 could be darlington drivers, Q2 is bias servo, and should be comparable in beta (Hfe) to be mounted with outputs for thermal stability. Make sure that the transistors you select have a breakdown Vce of at least 100V. I would say you may realistically get 90-100W RMS!

Q1 is an emitter follower, and has no voltage gain...but has a current gain. Rb should be a potentiometer(maybe 47K), and Rt (4.7K) might work, if servo is a darlington type device. As Q2 saturates it turns off the output bias. Turning Q2 off some will allow the outputs to bias class AB and also be linear as far as temp. coefficient.

I would use a current source\current mirror circuit for Ibias as it is more accurate.

Include negative feedback just like any other op-amp circuit, and referenced to ground(0V).

Get a cross reference book to determain the type of devices you may want to use for drivers and outputs. This dosen't look to complex, Good Luck!
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Old 6th August 2004, 03:41 AM   #6
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thanks u !

buy how kind i need to use for the darlingtons.......
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