Q.
Can the AD8302 gain/phase detector be used as a frequency discriminator?
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A.
If two signals of different frequencies are applied to the inputs of the AD8302, the output will be a triangle wave; similar to that shown in the TPC section of the data sheet (TPC’s 25-29; indeed, this is how these plots are generated). The frequency of this triangle-wave signal is equal to the frequency difference between the two input signals. The limit to the AD8302’s ability to determine the frequency difference is determined by the envelope bandwidth of the device. The envelope bandwidth is set by the capacitor on the PFLT pin.