Thermal Runaway

The maximum power dissipation in a transistor depends on transistor construction and may lie in the range from few mW to some Watts. The power dissipated in a transistor is predominantly the power dissipated at its Collector Base junction. Thus the maximum power dissipated at Collector base junction is limited by the temperature that can … Continue reading Thermal Runaway

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Millers Theorem

In general, the miller theorem is used for converting any circuit having the configuration of figure 2.48 (a) to another configuration shown in figure 2.48 (b) If $latex Z &s=2 &bg=ffffff$ is the impedance connected between two nodes, node 1 and node 2, it can be replaced by the two impedances $latex Z_1 &s=2 &bg=ffffff$ and $latex … Continue reading Millers Theorem

Stability Factors

$latex \displaystyle \Rightarrow &s=2 &bg=ffffff$ Stability factor indicates the degree of change in operating due to variation in temperature. There are three variables which are temperature dependent. We can define three stability factors : $latex \displaystyle S = \frac {\partial I_{C}}{\partial I_{CO}} \rightarrow \beta, V_{BE} &s=2 &bg=ffffff$  Constant $latex \displaystyle S^{'} = \frac {\partial I_{C}}{\partial V_{BE}} \rightarrow … Continue reading Stability Factors

Variation of Operating Point

>> Two important factors are two be considered while designing the biasing circuit which is responsible for shifting the operating point ($latex V_{CE}, I_{C} &s=2 &bg=ffffff$). TEMPERATURE Variation in ICO: The flow of current in the circuit produces heat at the junctions. This heat increases the temperature at the junctions. >> Minority carriers are temperature … Continue reading Variation of Operating Point

DC Load Line and Operating Point

>>  For Common Emitter configuration, output characteristic are : >>  DC Load line is plotted on output characteristic, graphically to calculate the DC values of $latex \displaystyle V_{CE} &s=2 &bg=ffffff$ and $latex \displaystyle I_C &s=2 &bg=ffffff$ >>  DC Load line obtained through KVL in output loop. $latex \displaystyle V_{CC} - I_{C} R_{C} - V_{CE} = 0 &s=3 &bg=ffffff$ $latex \displaystyle … Continue reading DC Load Line and Operating Point

Bipolar Junction Transistor (BJT)

$latex \displaystyle \Rightarrow  &s=2 &bg=ffffff$ Transfer + Resistor ⇒ Transistor $latex \displaystyle \Rightarrow  &s=2 &bg=ffffff$ It can be used either as an amplifier or as a switch. The basic amplify action is produced by transferring a current from low resistance to high resistance. $latex \displaystyle \Rightarrow  &s=2 &bg=ffffff$ BJT is three terminal (Emitter, Base, and … Continue reading Bipolar Junction Transistor (BJT)

Transistor Current Components

>>  The directions of actual currents in both NPN and PNP transistors are shown in the figure : ( Conventional currents direction always is taken outward to node )  Transistor current Components $latex \displaystyle I_{pE}, I_{nE}, I_{pC} &s=2 &bg=ffffff$  : The emitter current $latex I_{E} &s=2 &bg=ffffff$ consists of hole current $latex I_{pE} &s=2 &bg=ffffff$ (holes crossing from the … Continue reading Transistor Current Components