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


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