The circuit in the figure is an example circuit provided by ADI for converting a current DAC to a voltage DAC output. The subsequent amplification circuit is equivalent to a transimpedance amplifier. A typical application scenario is the interface section of a photodetector, converting the output of the photodetector into a voltage output.
Deriving the relationship between and .
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According to the “virtual short” concept, we know that
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Assuming the voltage at the DAC output node is , using Kirchhoff’s current law at the DAC output node, we can deduce that
Equation A:
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It is evident that
Equation B:
Equation C:
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By solving Equations B and C simultaneously, we obtain
Equation D:
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Substituting Equation B into Equation A, we get
Equation E:
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Substituting Equation D into Equation E, we find
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Simplifying gives us
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Thus,
References:
- How to Convert the Current DAC of DS1864 to a Voltage DAC | Analog Devices
