The $$\mathrm{{{{V_{OUT}}} \over {{V_{IN}}}}}$$ of the circuit shown below is

In the circuit shown below, D$$_1$$ and D$$_2$$ are silicon diodes with cut-in voltage of 0.7 V. $$\mathrm{V_{IN}}$$ and $$\mathrm{V_{OUT}}$$ are input and output voltages in volts. The transfer characteristic is

A sample and hold circuit is implemented using a resistive switch and a capacitor with a time constant of 1 $$\mu$$s. The time for the sampling switch to stay closed to charge a capacitor adequately to a full scale voltage of 1 V with 12-bit accuracy is ___________ $$\mu$$s (rounded off to two decimal places).

For a real signal, which of the following is/are valid power spectral density/densities?