summing multiple channel

Hi Analog!
I want to sum 4 channel output of ADA8282 "Radar receiver Path AFE: 4-Channel LNA PGA"

by op-amps and feed them to ARM cotrex-M7 microcontroller. though these channel are differential I want the final one as single ended, assume the bandwidth is 10MHz. I have seen some guideline from AD8333 "4 I/Q demodulator"

Since it told AD8333 output is in current format, I think this is not applicable in ADA8282 because it seems voltage output. :(

Summer and difference amplifier architecture are available in net like in electronic-tutorial.ws and other … . difference amp but it not talked about many tricky things that exist in real word.

Is difference amplifier like AD8270 and 4830-2 will do the job nicely? any explanation will appreciated

can you specify architecture for me? I think it must not be hard but I'm not familiar with Op-Amp.
Any help will appreciated.



a question about difference amplifier added.
[edited by: mohammadsdtmnd at 8:11 PM (GMT -5) on 27 Nov 2018]
  • 0
    •  Analog Employees 
    on Jan 9, 2019 3:29 AM over 2 years ago

    Hi mohammadsdtmnd,

    The AD8333 can still be used in your design by using the block diagram seen on Figure 53 of the AD8333 datasheet, you can used the AD8282 as the LNA for the input of AD8333 and use AD8021 as the TIA and summer to convert the output current of AD8333 to voltage that your micro controller accepts. With this design you can take advantage of the feature of AD8333, such as phase shifting that is commonly used in microphone beam forming application.

    Another option is that you can use a Difference amplifier to sum first the differential signal output of AD8282, you can use AD8270 or AD8274 to do this for its. On the datasheet of AD8274 you can refer to figure 41, that shows how you can sum two differential input with a gain of 2. The idea is that you need to first sum the differential output of AD8282 to convert the signal to single ended, then you can sum all the channels using AD8021. The output of the final summing amplifier will the be fed to the input of your ADC. 

    Just a reminder that to maximize the dynamic range of your ADC, the maximum output swing of your final summing amplifier should be equal or slightly less than the maximum input voltage of your ADC, to achieve this you can use resistor to attenuate the signal to the desired level.

    Regards,

    Joven