Merging DC and AC paths: behaviour of DAC8811IBDRB not clear
According to the design manual:
Simulations of this part of the design show that it is essential to have a very wide overlap frequency between the low and high frequency stages. It is relatively easy to set the amplitudes of the 2 signals the same by using the programmable attenuator in the LFA. To obtain an acceptably flat frequency response it is also necessary to minimise the effect of the phase shift in the low and high frequency signals at the high and low frequency roll offs.
The programmable attenuator is implemented using DAC8811IBDRB. Unfortunately DAC8811IBDRB shows a very big difference in bandwidth depending on the settings. From the schematics and simulation file (DAC8811 is not simulated), it is not clear how the effect of using DAC8811IBDRB (programmable attenuator) is compensated. Unfortunately, DAC8811IBDRB lacks a SPICE model.