Problem using a pair of AD8066 at I/V stage - diyAudio
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Old 22nd July 2008, 02:26 PM   #1
Noak is offline Noak  Singapore
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Default Problem using a pair of AD8066 at I/V stage

hi all,

I was working on a DIY CD player based on PCM1794. The differential signals are input to a pair of dual opamps at I/V, then going to the buffer stage via a single opamp at each channel. The supply voltage is +/- 9V. The i/V stage uses a 2200pf cap and 820ohm resistor for each signal path. The power supply pins are decoupled by 100nf caps.

I have no problems using AD8620 and AD8599 or a pair of op627 at the I/V stage but once I place in a pair of AD8066, there will be no sound at the output.

However, if I were to place only one AD8066 at either channel, I will have output signal. If I were to place one AD8066 while I use any other opamps at the other channel, I will have output signal as well. However, it will never work with a pair of AD8066. I have tried 4 known working AD8066 but to no avail.

What am I missing here?
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Old 22nd July 2008, 05:39 PM   #2
Mooly is offline Mooly  United Kingdom
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Circuit
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Old 25th July 2008, 03:51 AM   #3
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I use 8066 almost exclusively for I to V and haven't had any problems... without a diagram I suggest you check the input (current in) pins for any oscillations.... but definitely try to obtain and show us a circuit diagram.
Boky
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Old 25th July 2008, 10:50 AM   #4
Noak is offline Noak  Singapore
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Will definitely post the circuit once I've got it drawn out.
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Old 30th July 2008, 06:37 AM   #5
Noak is offline Noak  Singapore
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I have attached the schematic.
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File Type: jpg schematics.jpg (64.4 KB, 234 views)
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Old 30th July 2008, 06:54 AM   #6
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My guess is oscillations due to insufficient PS decoupling. Try placing elecrtolytic caps close to the PS pins of each IC and play with bypass values.
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Old 30th July 2008, 06:58 AM   #7
Noak is offline Noak  Singapore
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hi analog_sa,

Thanks for the prompt advice! I will proceed to try that out!
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