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Old 16th October 2008, 02:21 PM   #1
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Default tl072cn replaced by opa2134

Hi all,

I just replaced the TL072CN from my preamp with the "better" opa2134. The result is better highs more clear but the lows are not so punchy as with tl072cn. Is it me or this is the case? Any other experiances, or thoghts are welcome. Is this correct behaviour.
Attached the schematic.
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Old 16th October 2008, 03:21 PM   #2
AndrewT is offline AndrewT  Scotland
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check your schematic.
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Old 16th October 2008, 05:07 PM   #3
Mooly is offline Mooly  United Kingdom
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Have you tried to copy ( to draw ) the circuit from a piece of equipment or have you actually built it like the circuit shows
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Old 16th October 2008, 05:15 PM   #4
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kzeprf22,

It seems the opa2134 uses at least twice as much current as the TL072. What does the power supply for the OpA look like?

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Old 17th October 2008, 02:00 PM   #5
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Default re: tl072cn replaced by opa2134

Thank you all for the answers.

Quote:
Originally posted by AndrewT
check your schematic.
What do you see wrong in the schematic. Is anything wrong?

Quote:
Originally posted by Mooly
Have you tried to copy ( to draw ) the circuit from a piece of equipment or have you actually built it like the circuit shows
Both, It is a simple design that I builded many times. (non inverting amplifier)


Quote:
Originally posted by Patrik Floding
kzeprf22,

It seems the opa2134 uses at least twice as much current as the TL072. What does the power supply for the OpA look like?

Regards
Probably, but in the equipment I have tested this the supply is about 100VA 30.000 uf capacitance, LM337/17 regulation bypass capacitors.

The truth though is I done it a little bit quick this one, and I am thinking that something is wrong mechanicaly between the opamp base and the opamp. Maybe the opa is not conducting properly. I will check as soon as I find time and I will get back.

Thanks
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Old 17th October 2008, 03:33 PM   #6
Mooly is offline Mooly  United Kingdom
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R1 at 1 ohm does nothing. R2 puts an unwanted extra load on the opamp output. Omit it. C1 and R3, only you know
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Old 17th October 2008, 04:54 PM   #7
AndrewT is offline AndrewT  Scotland
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if this is supposed to be a unity gain topology then far too many components have been fitted.
If it's supposed to be a gain of 1.9times (+5.6dB) then R2 is attached to the wrong node.

I think the output resistor of 75r is necessary since the tl07x series are reputed to be very bad at driving capacitive loading. The 75r should be located right next to the output pin of the opamp.

If R1=1k0 then it is there to minimise output offset by providing a resistive route for the input offset current. But 1r0 does nothing and even 1k0 will hardly change the output offset since tl07x are FET input opamps.
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