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Oscillation from Tank Circuit If there were no losses in the tank circuit to consume the energy the interchange of energy between inductor (L) and capacitor © would continue indefinitely. But in practical tank circuit there are resistive and radiation losses in the coil and dielectric losses in the capacitor. Due to these losses the oscillating waveform gradually decreases and eventually it becomes zero. In order to make the continuous oscillation in the tank circuit, it is necessary to supply correct amount of energy to the tank circuit at the proper time intervals. The polarity of the applied energy must confirm the existing polarity. Therefore in order to make the oscillations in the circuit undamped (continuous), the following conditions must be fulfilled. The amount of energy supplied should be such so as to meet the losses in the tank circuit and the AC energy removed from the circuit by the load. The applied energy should have the same frequency as that of the oscillation in the...

Errors in Moving Coil Instruments The errors that usually occur in PMMC instruments are 1.        The frictional error. 2.        Temperature error. 3.        The error owing weakening of permanent magnet. 4.        Stray magnetic field error. 5.        Thermo-electric error. 6.        Observational error. 1.        The frictional Error: The friction of the pivot in the jewel produces a frictional torque which affects the instrument reading. This error is more serious for sensitive instruments designed for low operating torque. Remedy: The frictional error in PMMC instruments can be produced by providing proper pivoting and balancing i.e. these errors may be reduced by adopting a moving system of light construction and large deflecting torque. 2.      ...

Stabilization When the temperature changes or the transistor is replaced the operating point also changes. However for faithful amplification, the operating point must be remains fixed. This necessity to make the operating point independent of these variations. The process of making operating point independent of temperature changes or variations in transistor parameters is known as stabilization. Thus for maintaining the operating point independent of these variations, the following techniques are used. They are 1.        Stabilization technique 2.        Compensation technique Need of Stabilization The following are the factors that effect the stability of the operating point. 1.        Temperature dependence of I C 2.        Change of V BE and β due to replacement of transistor 3.        Thermal runway 1.     ...