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Old 22nd February 2004, 11:23 AM   #1
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Default I/V conversion idea

Hi,

just a very vague idea and maybe nothing new:

How about connecting the DAC output to the output of an op amp ?

The op amp output provides virtual ground, it's + input is tied to ground.

Voltage swing is seen across resistors in the op amp rails.



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Old 22nd February 2004, 12:16 PM   #2
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Default Re: I/V conversion idea

Quote:
Originally posted by Bernhard
Hi,

just a very vague idea and maybe nothing new:

How about connecting the DAC output to the output of an op amp ?

The op amp output provides virtual ground, it's + input is tied to ground.

Voltage swing is seen across resistors in the op amp rails.



Bernhard

I think that it will work...try it!!

Tell us about the sound quality

PS: The output is even balanced...i'm curius!...
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Old 22nd February 2004, 12:35 PM   #3
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Just how to control offset ?
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Old 22nd February 2004, 12:37 PM   #4
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Quote:
Originally posted by Bernhard
Just how to control offset ?
The opamp must have the feedback resistors...as usully...only nothing connected to the input...
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Old 22nd February 2004, 01:40 PM   #5
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Quote:
Originally posted by Tube_Dude


The opamp must have the feedback resistors...as usully...only nothing connected to the input...
I meant the I/V output, not the input...

A quick & dirty schematic, the 3,75k used to simulate the 4mA current.

Again, maybe nothing new but as I am new to I/V, I don't know.

Can be built discrete too and without output cap...

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Old 22nd February 2004, 01:54 PM   #6
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Quote:
Originally posted by Bernhard


I meant the I/V output, not the input...

A quick & dirty schematic, the 3,75k used to simulate the 4mA current.

Again, maybe nothing new and can be built discrete too and without output cap...

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I was thinking that that the current output of the dac was connected straight to the op amp output...
that way no offset to care...and the output will be in resistors in series with supply pins of the op amp...
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Old 22nd February 2004, 02:00 PM   #7
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Yes, I was thinking like this too, but then the signal is cut in positive and negative halfs and has to be put together again somehow.

On a sine current input there will be only a positive halfwave on the positive rail resistor.
And negative rail resistor respectively.
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Old 22nd February 2004, 02:03 PM   #8
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Quote:
Originally posted by Bernhard


On a sine current input there will be only a positive halfwave on the positive rail resistor.
And negative rail resistor respectively.

Not if you force the op amp to work in class A by a pull down resistor from the power rail ...
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Old 22nd February 2004, 02:18 PM   #9
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Quote:
Originally posted by Bernhard
Yes, I was thinking like this too, but then the signal is cut in positive and negative halfs and has to be put together again somehow.

On a sine current input there will be only a positive halfwave on the positive rail resistor.
And negative rail resistor respectively.
Biasing the op amp into class A with CCS at the o/p will give full o/p on one of the supply lines.

mike

just realised this will not be practical - tube dude's idea may be better
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Old 22nd February 2004, 02:20 PM   #10
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Quote:
Originally posted by mikelm


Biasing the op amp into class A with CCS at the o/p will give full o/p on one of the supply lines.

mike

Yes...the CCS is even better than the resistor....and will inject much less suplly noise!
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