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

Negative feedback in

1. Voltage series configuration
2.Current shunt configuration

(a) increases input impedance
(b) decreases input impedance
(c) increases closed loop gain
(d) leads to ascillation.

Consider the circuit given in fig. using an ideal operational Amplifier.

The characteristics of the diode are given by the relation I = I_s $$\left[ {{e^{{{qV} \over {KT}}}} - 1} \right],$$

Where V is the forward voltage across the diode
(a)Express V₀ as a function of V_i assuming V_i> 0.
(b)If R = 100K$$\Omega $$ , I_s = 1$$\mu $$A and $${{KT} \over q}\,\, = \,\,25mV$$

An IC 555 chip has been used to construct a pulse generator. Typical pin connections with components is shown below in fig. for such application. However it is desired to generate a square pulse of 10KHz.. Evaluate values of $${R_{A\,}}$$ and $${R_{B\,}}$$ and if the capacitor has the value of 0.01$$\mu $$F for the configuration closed. If necessary you can suggest modifications in the external circuit configuration.