An Amplifier a has 6 dB gain and 50 $$\Omega $$ input and output impedances. The noise figure of this Amplifier as shown in the figure is 3 dB. A cascade of two such Amplifiers as in the figure will have a noise figure of

The circuit shown in the figure is that of

In the given circuit if the voltage inputs V- and V+ are to be Amplified by the same Amplification factor, the value of 'R' should be

An op-Amp is used as a zero-crossing detector. If maximum output available from the Op-Amp is $$ \pm 12\,\,{V_{p - p}}$$ and the slew rate of the Op-Amp is 12 $$V/\mu $$ sec then the maximum frequency of the input signal that can be applied without causing a reduction in the P-P output is _____