AD9613 input driver question


I'm driving the AD9613 analog inputs from the ADA4930 differential amplifier.

I've looked at figure 47 of AD9613. It seems there is some mistake, since the FB+ (without dot) should be connected to IN-, and FB- (with dot) should be connected to IN+ to operate as an amplifier (by using negative feedback). This is also true according to AD9613 datasheet and according to simulations.

I'm quite sure there is a mistake at figure 47, but I would like to get some approval from Analog Devices.

Please notice, there are some other ADCs with the same issue at the datasheet.

Also notice, that not all differential amplifiers proposed will completely fit the AD9613 ADC (for example: ADA4937 will accept OCM from 1.2V - 2.1V, while the AD9613 outputs 0.9V bias).

Best regards


  • +1
    •  Analog Employees 
    on Aug 31, 2018 10:03 AM over 2 years ago

    Hi Alex,

    Thank you for pointing this out. You are right, IN+ and IN- pins were interchanged. We will have the necessary corrections.

    For the VoCM limitations of the ADA4937 (1.2V - 2.1V), this is specified at 3.3V supply. This, however, can be varied and can be lowered down to 0.9V to cater the VCM requirement of the ADC thru Power Supply variations as long as it is within the operating range of the FDA. Vocm of ADA4937 is specified to be (Vs- + 1.2) to (Vs+ - 1.2), and few modifications on the supply the 0.9V VCM can be met. With that being said, ADA4930 would be the easiest driver to drive Pipeline ADCs which requires 0.9V.



  • By the way ... I've paid an attention to the caption of figure 47 ... " Figure 47. Differential Input Configuration Using the ADA4938-2 " While the OpAmp shown is ADA4930-2.

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