I'm making an Arbitrary Waveform Generator and need some advice with impedance matching after the output filter.
Analog stuff really isn't my area. :-)
I have a 7 order low-pass with a terminating impedance of 50 Ohm. Filter is fed by an op-amp.
Simulating shows a nice curve with a cutoff as expected.
Removing the terminating 50R or adding another in parallel obviously make the curve go all bonkers.
The question is now - should I drop the (internal) 50R load and require that the output is connected to nice 50R inputs through nice and shiny 50R cables, or add an internal 50R load, and thereby allowing more freedom for the output connection?
* I've seen that terminating with 25R looks way better than no termination at all.
* As this is not an instrument that mostly will be used in nice labs with nice cables it will more often than not be connected to high impedance inputs.
The above seems to indicate I should terminate internally with 50R.
Obviously, I could also have a switch that connects/disconnect that 50R load res.
Are there other/better ways to handle this?
Any suggestions ?