AD633 offset and supply

Hello,

I need some help with my circuit. 2 sine waves are generated with 2 AD9833's, then are amplifier and filtered with 2 1st order low pass filters, and then connected to the AD633. As the sine wave have about 200 mV offset, I'm using 2 coupling capacitors, but there's still some offset. I must use the "Optional Offset Trim Configuration" on both inputs (X2 and Y2).This configuration only uses resitors. Should i use a voltage divider and a buffer for each input?

Is there any problem if I use a dc-dc converter (LT1054 inverter) to get -Vcc?

Thank you

PS : Sorry for my english



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[edited by: inigoatm at 1:03 PM (GMT -4) on 5 Sep 2020]
  • 0
    •  Analog Employees 
    on Sep 10, 2020 12:20 AM

    Hi,

    If I understand it correctly, your input is coming AD9833 which are single ended but with 200mV offset and will be feed to
    X1 and Y1 of AD633.


    You can use this Offset Trim Circuit of figure 11 to compensate this offset and feed to X2 and Y2.
    For the example circuit, it is limited to +/-50mV compensation and that is the Voltage divider of 300k and 1k resistor with +15/-15v Vs.
    You need a compensation of 200mV, therefore you must replace the 1k to a higher value.

    Also, you will need 1 circuit per 1 input.
    1 offset trim circuit for X2, and another 1 offset trim circuit for Y2.

    For the supply.
    You will just need to comply the supply requirements of the AD633 and make sure its has enough current to make the device power up and functional.

    Thanks and regards.