svensl
Full Member level 1
Hello all,
I have a 3V i/p signal coming from an external RC pole (500Hz). The external resistance of the RC pole is not fixed but assumed to be in the 1k region. After the "almost" dc signal is passed on chip it needs to be divided down by 2 as power supply is 1.5V. It then feeds into a sigma delta modulator (continuous time RC). The RC time constant uses 200kOhms and 10pF.
My problems is the divide by two. If I choose low resistance values for my divider then the external 1k Resistor will load it too much. If I make the divider resistors bigger then it will effect the resistance used in the integrating amplifier.
Now essentially it needs a buffer. But it would have to be rail-to-rail input and output.
Is there an easier way to implement the mentioned scenario without loading effects?
Thanks,
I have a 3V i/p signal coming from an external RC pole (500Hz). The external resistance of the RC pole is not fixed but assumed to be in the 1k region. After the "almost" dc signal is passed on chip it needs to be divided down by 2 as power supply is 1.5V. It then feeds into a sigma delta modulator (continuous time RC). The RC time constant uses 200kOhms and 10pF.
My problems is the divide by two. If I choose low resistance values for my divider then the external 1k Resistor will load it too much. If I make the divider resistors bigger then it will effect the resistance used in the integrating amplifier.
Now essentially it needs a buffer. But it would have to be rail-to-rail input and output.
Is there an easier way to implement the mentioned scenario without loading effects?
Thanks,