ADA4950 single-ended input with DC-offset to differential output AD9094

Thank you for your very detailed response Peevee it is very appreciated!

This makes more sense now. So you would recommend AC coupling both inputs, AC coupling the outputs, connect VOCM to the midlevel of VS+ (thus midlevel of 3.3V) and use the internal internal VCM to bias the AC coupled output of the ADA4950?

Would you be able to share the LTSPICE simulation model?

Also as a final request, could I send another screenshot of my schematic today just to be sure that everything is well? (as mistakes cannot be happening in this design)

Hi MikeHuisma,

If it is OK not to use differential amplifier in your application, you can check the analog input configuration from the AD9094-1000EBZ (same board used for AD9694EBZ) and consider if BALUN input will work for your requirement.
You can download the design files for the board here: EVALUATING THE AD9094 ANALOG-TO-DIGITAL CONVERTER [Analog Devices Wiki]

You can get the spice model of ADA4950-2 here: ADA4950-2 Datasheet and Product Info | Analog Devices
For the simulation I showed, I used the ADA4950-1: ADA4950-1 Datasheet and Product Info | Analog Devices

Feel free to share your schematic again

If you want to discuss including the details of your project offline, you can send me an email.

Best regards,
Peevee

Hi MikeHuisma,

If it is OK not to use differential amplifier in your application, you can check the analog input configuration from the AD9094-1000EBZ (same board used for AD9694EBZ) and consider if BALUN input will work for your requirement.
You can download the design files for the board here: EVALUATING THE AD9094 ANALOG-TO-DIGITAL CONVERTER [Analog Devices Wiki]

You can get the spice model of ADA4950-2 here: ADA4950-2 Datasheet and Product Info | Analog Devices
For the simulation I showed, I used the ADA4950-1: ADA4950-1 Datasheet and Product Info | Analog Devices

Feel free to share your schematic again

If you want to discuss including the details of your project offline, you can send me an email.

Best regards,
Peevee

Hi Peevee,

Thank you again for your response! I have updated the schematic according to your insight and now have the following:

I have AC-coupled the input and routed it to INB+ (because when routing it to INA+ the output signal seemed to be half the input signal and INB+ amplifies it by 2). By having a 5V power supply with a VOCM of half this power supply (2.5V) the swing is well within the range of the amplifier.

Then I AC-couple the output of the amplifier and provide ADC+ and ADC- to the input of the AD9094. As you suggested I will use the internal common mode biasing of the ADC.

What do you think of this?

Hi Peevee,

My apologies for asking this much of you but would you be able to take a look at the schematic I posted here yesterday today and have a quick look on how I've now implemented it?

Hi MikeHuisma,

MikeHuisma said:

I have AC-coupled the input and routed it to INB+ (because when routing it to INA+ the output signal seemed to be half the input signal and INB+ amplifies it by 2). By having a 5V power supply with a VOCM of half this power supply (2.5V) the swing is well within the range of the amplifier.

The AC coupling seems okay. About the signal being half, this is due to the resistor combination R5 to R10 before the ADC+/- .

If you try to probe the OUT+/- pins you should see proper Gain = 1 if you're connected to INA+

Best regards,
Peevee