AD8314, V_UP - FILT, how to be choice of CF and series resistor ?

Hi all,

In the datasheet page 13, following is comment.

The video bandwidth is related to CF by

Video Bandwidth = 1 / 2 π × 13 kΩ × ( 3.5 pF + CF )

In the datasheet page 14, following is additional comment.

In practice, an improvement in loop dynamics can often be achieved by adding a response zero, formed by a resistor in
series with CF.

How to decide RC filter (Rs : series resistor) value ?

Video Bandwidth = 1 / 2 π × ( 13 kΩ + Rs ) × ( 3.5 pF + CF ) ?

Is it correct ? 

Best regards,


  • 0
    •  Analog Employees 
    on Jun 12, 2018 7:14 PM over 2 years ago

    Adding a zero in the loop is in the context of a power amplifier control loop.  The video BW equation given for the application shown in Figure 31, does not need the addition of a zero.

    The choice of the zero would be power amplifier and application dependent, therefore no singular closed-form equation is given.  Choice of the zero would be the responsibility of the user and most likely require and iterative experimental approach to attain loop dynamics desirable to the user.