I am currently using the LTC6090 in a precision, unity gain instrumentation amplifier mode at its maximum operating voltage (with a voltage limiter) to drive a ADA4254 VGA (in a prototype system). This is a DC coupled system, with relatively low bandwidth (<10kHz). Unfortunately, the ADA4254 does not have the same voltage range as the LTC6090, and as a result I am not able to use the full dynamic range of my system. In my application, the dynamic range of the system is quite large, and as a result there are situations where I will need to precisely amplify or attenuate the signal coming out of the LTC6090 before going into an ADC. The architecture of the ADA4254 provides the gain range choices I need, but not the voltage range; it is a +/-28V circuit.
I have looked at a variety of different topologies for digitally controlled variable gain instrumentation amplifiers, but all of them are oriented around low voltage gain control circuits, or have the potential for high gain error. Thus far, I have not been able to find another amplifier circuit/product that does both gain and attenuation in the voltage range I am using. I would like to find another digitally controlled, instrumentation amplifier circuit/product that allows me to use a the full dynamic range of the LTC6090.
Or, is this something I am going to have to design from scratch?
Eventually, I would like to transition to using the ADHV4702-1, which has an even higher voltage requirement.
Do you have any suggestions?