I guess this is a rather easy question for you, but unfortunately I do not know the answer.
I must apply a control voltage to a VCO in order to generate a frequency modulated signal. My idea was to generate this voltage with a DAC and a lowpass filter, because it has to rise linearly between 0 – 3 Volts within 1 milli sec and then fall back to 0 volts in the same time. When I take e.g. the DAC7821 which is fast enough for the task, the output is a current (as for all DAC which would be fast enough).
My question is, can I simply put a current-to-voltage converter after the DAC? If so, which OpAmp is recommended for this task?
Thank you for helping me,
What DAC are you interested in using? Have you checked out the datasheet application section of the DAC in question? Most of our DACs that have current output should have an application circuit in the datasheet that shows the current to voltage conversion and as example device. For instance, DAC8806, in the application section of the datasheet (pg 13 - Figure 39), an example circuit is shown using the OPA277.
This is just an example; there are a lot of different variables that you would need to consider given your specific application that could determine what op-amp is the best fit.
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Precision Data Converters
A milli-second is a good amount of time. You may be able to get by using a voltage output DAC. Try looking at some of our string DACs, such as the DAC8560 and DAC8562, they settling time (including slew rate time) is on the order of 10us and do include an internal reference voltage. You wll just need to make sure that they meet the linearity requirement that you are looking for. Otherwise, a current MDAC with a transimpedance amplifier would work as a multichip solution.You will care about bandwidth, slew rate, settling time, and input and output limits of the amplifier when choosing the right one.
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