- Question A Explain Three Conditions That Must Be Fulfilled In Order To Make The Oscillations In The Tank Circuit Undamp 1 (47.99 KiB) Viewed 48 times
Question a) Explain three conditions that must be fulfilled in order to make the oscillations in the tank circuit undamped. b) Explain how a positive feedback amplifier can act as an oscillation. c) A 1 mH inductor is available. Choose the capacitor values in a Colpitts oscillator so that f-2 MHz and my=0.35. d) Explain the Barkhausen criterion and show mathematically how it solves the problem of damped oscillations in the tank. e) Calculate the operating frequency and feedback fraction for the Hartley oscillator shown in the figure below. The mutual inductance between the coils, M= 30 H. + Vec RF CHOKE HI 1000μH4 REC 100 μH C-20 pF You Question a) Explain briefly the performance quantities of power amplifiers stating how they help to determine a good amplifier from a bad one. b) Prove that the efficiency of a class A amplifier is 25% (directly coupled). c) Briefly explain the following terms as applied to power amplifies (i) Thermal runaway. (ii) Heat sink. e) A directly coupled class A amplifier shown below operates with an applied sinusoidal input signal generates a base current of 5mA rms. Using Ra as 1.5K2, calculate Quiescent current Ico - Quiescent voltage Vero iii. input power iv. Output power v. Collector efficiency and comment.