Bipolar-Junction-Transistor

A bipolar junction transistor consists of three regions of doped semiconductors. A small current in the center or base region can be used to control a larger current flowing between the end regions (emitter and collector). The device can be characterized as a current amplifier, having many applications for amplification and switching

A transistor in a circuit will be in one of three conditions

Cut off (no collector current), useful for switch operation.
In the active region (some collector current, more than a few tenths of a volt above the emitter), useful for amplifier applications
In saturation (collector a few tenths of a volt above emitter), large current useful for "switch on" applications.

Collector Current Determination

The base-emitter voltage

can be considered to be the controlling variable in determining transistor action. The collector current is related to this voltage by the Ebers-Moll relationship (sometimes labeled the Shockley equation):

where

T = absolute temperature
k = Boltzmann's constant
e = electron charge

The saturation current is characteristic of the particular transistor (a parameter which itself has a temperature dependence). This relationship is stable over a wide range of voltages and currents. A further useful relationship is

where

can be called the current gain. The value of

is not highly dependable since it depends on

and the temperature.

Download the pdf file

Comments

Armature Winding ,Pole Pitch, Coil Span, Commutator Pitch

Now we are going to discuss about armature winding in details. Before going through this section, we should understand some basic terms related to armature winding of dc generator . Pole Pitch Definition of Pole Pitch The pole pitch is defined as peripheral distance between center of two adjacent poles in dc machine. This distance is measured in term of armature slots or armature conductor come between two adjacent pole centers. This is naturally equal to the total number of armature slots divided by number of poles in the machine. If there are 96 slots on the armature periphery and 4 numbers of poles in the machine, the numbers of armature slots come between two adjacent poles centers would be 96/4 = 24. Hence, the pole pitch of that dc machine would be 24. As it is seen that, pole pitch is equal to total numbers of armature slots divided by total numbers of poles, this can alternatively referred as armature slots per pole . Coil Span or Coil Pitch Coil of ...

Propagation-Radio-Waves

Radio Wave Propagation types

Winding Factor | Pitch Factor | Distribution Factor

Before knowing about, winding factor , we should know about pitch factor and distribution factor , as winding factor is the product of pitch factor and distribution factor . If winding factor is denoted by K w , pitch factor and distribution factor are denoted by K p and K d respectively, then, k w = k p k d . The pitch factor and distribution factor are explained below one by one. Pitch Factor In short pitched coil, the induced emf of two coil sides is vectorically added to get, resultant emf of the coil. In short pitched coil, the phase angle between the emfs induced in two opposite coil sides is less than 180° (electrical). But we known that, in full pitched coil, the phase angle between the emfs induced in two coil sides is exactly 180° (electrical). Hence, the resultant emf of a full pitched coil is just arithmetic sum of the emfs induced in both sides of the coil. We well know that, vector sum or phasor sum of two quantities, is always less than their a...

Electrical Engineering

Search This Blog

300x250 Ads