Problem using a pair of AD8066 at I/V stage

Noak · 22nd July 2008, 02:26 PM

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?

Mooly · 22nd July 2008, 05:39 PM

Circuit

Extreme_Boky · 25th July 2008, 03:51 AM

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

Noak · 25th July 2008, 10:50 AM

Will definitely post the circuit once I've got it drawn out.

Noak · 30th July 2008, 06:37 AM

I have attached the schematic.

analog_sa · 30th July 2008, 06:54 AM

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.

Noak · 30th July 2008, 06:58 AM

hi analog_sa,

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

22nd July 2008, 02:26 PM	#1
Noak diyAudio Member Join Date: Jul 2005 Location: Singapore	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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22nd July 2008, 05:39 PM	#2
Mooly diyAudio Member Join Date: Sep 2007	Circuit

25th July 2008, 03:51 AM	#3
Extreme_Boky diyAudio Member Join Date: Dec 2003 Location: Sydney	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

25th July 2008, 10:50 AM	#4
Noak diyAudio Member Join Date: Jul 2005 Location: Singapore	Will definitely post the circuit once I've got it drawn out.

30th July 2008, 06:54 AM	#6
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	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.

30th July 2008, 06:58 AM	#7
Noak diyAudio Member Join Date: Jul 2005 Location: Singapore	hi analog_sa, Thanks for the prompt advice! I will proceed to try that out!

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