Thoughts on this DAC reconstructions filter circuit?

Thread Starter

I_love_dsp

Joined Apr 16, 2022
2
I've altered a reconstruction filter circuit to use the LTC728XT instead of the AD8608 op-amp used in the example circuit below.

This is being used as part of a dsp project and the recommended AD8606 is end of line from what I gather + way too expensive. I'll need 4 outputs hence the decision to use an op-amp with 14 pins.

Is anyone able to see any issues with my attempt?

Example circuit
Example filter circuit


Altered version

1650113710679.png

Thanks in advance
 

crutschow

Joined Mar 14, 2008
29,818
I see no obvious problem with changing the op amp.
There may however, be a slight change in the filter response since you are going from a 10MHz to a 1MHz bandwidth op amp.

But is the DAC-Out signal positive since, with a single supply, the op amp output can only go positive?
 

Thread Starter

I_love_dsp

Joined Apr 16, 2022
2
Hi @crutschow , yes the DAC-out has a DC offset of 1.5V. Just to clarify, I plan to use the 14 pin LTC728 which looks to be 11MHz and not 1MHz or have I misinterpreted the datasheet?
 

DickCappels

Joined Aug 21, 2008
8,711
I hope you will be able to replace the opamp if it turns out that 11 MHz has insufficient gain-bandwidth for your application. It may help to roll off the DAC output with a passive RC filter first. A good SPICE simulation with a good model of the opamp would probably be helpful right now.
 
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