A physical unclonable function (PUF) device includes a ring oscillator, a plurality of band-pass filters, a demultiplexer, and a latch. The ring oscillator generates a frequency signal. Each passive band-pass filter performs filtering on the frequency signal to pass the frequency signal or block the frequency signal. The demultiplexer receives a set of challenge bits and delivers the frequency signal to a selected passive band-pass filter among the plurality of passive band-passed filters based on the challenge bit. The latch outputs a response bit in response to the filtering performed by the selected passive band-pass filter.