Of the four biasing circuits shown in Fig. For a BJT, indicate the one which can have maximum bias stability:

A signal of bandwidth 3.5 kHz has peak-to-peak and rms amplitudes of 4 V and 0.2 V, respectively. This signal is passed through a linear PCM coder and then transmitted over a channel capable of supporting a transmission rate of 60 kbps. Calculate the maximum signal-to-quantization-noise ratio that can be obtained using this system.

A part of a communication system consists of an amplifier of effective noise temperature, $$Te = \,\,21\,\,{}^ \circ K\,$$, and a gain of 13 dB, followed by a cable with a loss of 3 dB. Assuming the ambient temperature to be $$300{}^ \circ \,K$$, we have for this part of the communication system,

Zero mean Gaussian noise of variance N is applied to a half wave rectifier. The mean squared value of the rectifier output will be: