Hero999
Banned
I've just had an idea, forgive me if this is old news but rather than biasing at ½Vref use a precision rectifier and comparator.
The comparator will provide a high/low signal indicating whether it's + or -.
The precision rectifier shown here (for which I take no credit, I found the circuit on the datasheet for an op-amp) has the advantage of only needing a single supply, although it has a loss of 2.
Using a precision rectifier has the advantage of effectively doubling the precision of the ADC.
If hysteresis is added to the comparator, it should be < the V/bit of the ADC. In this example 22k/10M×5 = 11mV so for a 8-bit DAC is fine 5/256 = 19.53mV.
The comparator will provide a high/low signal indicating whether it's + or -.
The precision rectifier shown here (for which I take no credit, I found the circuit on the datasheet for an op-amp) has the advantage of only needing a single supply, although it has a loss of 2.
Using a precision rectifier has the advantage of effectively doubling the precision of the ADC.
If hysteresis is added to the comparator, it should be < the V/bit of the ADC. In this example 22k/10M×5 = 11mV so for a 8-bit DAC is fine 5/256 = 19.53mV.
Attachments
Last edited: