I am working on a project that requires sampling noise over a large dynamic range. The ADC's 12 bit resolution doesn't seem to be enough so we are looking for a low cost way to increase it.
The obvious answer is a log amplifier but they do add cost. As an alternative has anyone tried using two ADCs sampling simultaneously, one with gain and one without?
Our signal is low pass filtered to 5KHz. The plan would be to sample it twice simultaneously with the ADCs triggered by an event. One ADC would have a gain of 1, the other a gain of 64. For large signals the high gain ADC would be saturated and the unity gain ADC would be used for the reading. For small signals the high gain ADC would be used.
We have a 2.048V reference so get 0.5mV/LSB from a unity gain ADC. A 64 gain ADC would be able to measure down to 7.8nV/LSB.
Has anyone tried this? Is it madness? :-)