Question
I use the AD9838 to generate a sin-wave and I want to be able to control the output amplitude. For this I like to use the FSADJUST pin and instead ofusing a fixed resistance use a digital pot (like AD5175BRMZ-10) or, preferably, use your DAC (AD5663ARMZ) together with an OP and a BJT to set thecurrent drawn on the FSADJUST pin. However, I am not sure if the AD9838 will work in this way? How large is the range I can use for the current? Ifind the max current to 3mA in the data sheet but what is the minimum?
Answer
We have a similar setup with AD9834 where a DAC is used to drive the FSADJUST pin.
Find below the link to the description about the circuit.
http://www.analog.com/en/design-center/reference-designs/hardware-reference-design/circuits-from-the-lab/cn0156.html#rd-overview