Signal And Systems

(b) Derive the conversion efficiency of a class B power amplifier and clearly explain the reasons, why are most of the power amplifiers used in practice designed to operate in class AB stage?

(a) Write down the classification of a power amplifier. Draw circuit diagram and their characteristics also. 

(b) Calculate the minimum value of Vos required for an NMOSFET to operate in pinch off condition when V_os =1V, V_p =2V, 1_DSS =10 mA. Also find the corresponding drain current. 

Write short note on the following:

(b) Harmonic distortion

Write short note on the following:

(a) Cross over distortion

(d) Let x₁ (n) and x₂(n) bt the periodic sequence with period N and their 

D.T.F.S. given by  . show that the sequence  can be expressed as 

(c) If    What relationship exist between a_n, b_n and c_n 

(b) For a LTI system, prove that condition for stability i.e. 

(a) Determine and sketch the even and odd parts of the signals given below.

(D) A UJT relaxation oscillator has R_E =60 KN and C =0.25 .Determine the pulse repetition frequency. Take intrinsic stand-off ration to be 0.65.

(a) Sketch and explain the Silicon Controlled Rectifier characteristics with the switching action.

(e) Show that the energy (power) of a real valued signal is equal to the sum of the energies (powers) of its even and odd components. 

(a) Explain the meaning of pinch off voltage in a JFET. How does the current flow in a JFET after pinch off? Also explain the meaning of the terminologies:

(i) Trans-conductance

(ii) Drain Resistance and

(iii)Amplification Factor 

(c) The open loop gain of an amplifier changes by 5%. If 10 dB negative feedback is applied, calculate the percentage change in the closed loop gain. 

(b) Why voltage series feedback is most commonly used in cascaded amplifier?

(a) How the negative feedback changes the impedances? Explain with mathematical expression. 

(a) Let x(t) and y(t) be periodic signals with fundamental period T and Fourier series coefficients ax and bk respectively. Derive the Fourier series coefficients of the following signals.

(i) .    (ii) 

(b) Prove the distributive property of the convolution for continuous time systems.

(a) indicate whether the following systems are (i) Static/Dynamic

(ii) Linear/Non-Linear (iii) Time-variant/Time-invariant (iv) Causal/Noncausal (v) Stable/Unstable.

(1) y(n) = x(n).u(n)                 (2) y(n + 1) = x²(n +x1) + x(n-1)

(3) y(n) =                      (4) y(n) = x(-n+2) 

(b)  and  .Compute and plot each of the following convolutions

(i) (ii) 

(a) Consider the discrete time signal.Determine the values of the integers M and n_o so that x(n) may be expressed as x(n) = u(nM -n₀).