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Old 9th September 2004, 05:13 PM   #1
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Question DRV134 Input Resistor & Opamp Output Questions

I'll be using some DRV134s in my pre for a balanced out and while routing the board today, I checked the datasheet once more just to be sure I didn't make any stupid mistakes.

In the datasheet there isn't any resistor shown on the input of the DRV134, so I suppose it isn't necessary to use one, right? Or would it be safer to add one?

Next question, I can't seem to find an answer for this one. Take a look at the attached image. The opamp on the left controls the gain, the output resistor is to avoid oscillations. But how do I handle the output to the 2 DRVs & 2 opamps (the chips on the right)? Is my scheme with the resistors correct or not?
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Old 11th September 2004, 12:19 AM   #2
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* bump*
No one?
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Old 15th September 2004, 05:34 PM   #3
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Ah, c'mon, 75 read my question and not one of them can help me out?

Think ! Help me !
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Old 15th September 2004, 07:15 PM   #4
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Default Re: DRV134 Input Resistor & Opamp Output Questions

Quote:
Originally posted by Devil_H@ck

In the datasheet there isn't any resistor shown on the input of the DRV134, so I suppose it isn't necessary to use one, right? Or would it be safer to add one?

Next question, I can't seem to find an answer for this one. Take a look at the attached image. The opamp on the left controls the gain, the output resistor is to avoid oscillations. But how do I handle the output to the 2 DRVs & 2 opamps (the chips on the right)? Is my scheme with the resistors correct or not?
You should ask several of these questions to TI's support.

You don't need any resistor at the input of the DRV134, but you will need a blocking cap if there's any DC.


Carlos
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Old 15th September 2004, 07:45 PM   #5
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Ok, so no input resistors to the DRVs, thanks!

Are the resistors for the 2 opamps correct? I think they are, but I'm not 100% sure.
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Old 15th September 2004, 09:46 PM   #6
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Devil guy,

I looked at your diagram, not sure what you want to do. In both cases I see unbalanced outputs, if you need balanced outputs you must invert one of the pair of outputs. What is in those squares with the + sign?

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Old 15th September 2004, 10:38 PM   #7
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Not sure what the little boxes are (BUF634 perhaps), but I'm pretty sure the big boxes are the DRV134's which are quite nice unbalanced to balanced converters from ti.
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Old 15th September 2004, 10:41 PM   #8
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Your concept for splitting the signal looks fine to me.
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Old 16th September 2004, 01:04 AM   #9
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janneman, Tim_x got it right, the small boxes with the + sign in it are BUF634s, the big boxes are DRV134s. I left out the values to make the schematic easier to read.

Thx, Tim_x .

* Oh, btw, I believe there is a flaw in that schematic, I've changed it in the version on my PC. The JFET biassing cascode should be after the BUF634, on the output, since that's where the feedback to the opamp is taken.
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Old 16th September 2004, 03:57 AM   #10
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The purpose of the cascode is to draw a constant current from the output devices in your opamp, so unless you want to bias your BUF634's into class A they should be right on the opamp output.
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