A specified amount of current is allowed to flow through the diode. if the current passing through the diode exceeds the specific value, the diode gets heated and is likely to be damaged. therefore in a biasing circuit a resistance R has been applied , which limits the current passing through the diode within a specific value.
The emitter bias circuit is called self-bias because the bias voltage across the emitter-resistor is based on the transistor's own characteristics. The bias voltage adjusts itself based on the varying collector current to stabilize the operating point of the transistor. It is a self-adjusting mechanism that helps maintain a stable bias point for the transistor.
emitter bias provides a feedback to the circuit so that circuit remains in linear regionn
In a reverse bias condition of a circuit current initially remains the same for low voltage but at the breakdown voltage current increases fast even for a small increase in voltage.hence.........
it is a switching device that need a current..so u will need a resistor to open the switch..
This is an overcurrent condition, correct? The real answer is, "well, it's not SUPPOSED to open!" Which is true--if the emitter resistor opens, the smoke (which, as we all know, is the thing that makes electrical devices work) gets out and the circuit stops working. If you're in an overcurrent condition sufficient to destroy parts and you don't lose the resistor, the transistor being serviced by the emitter resistor is destroyed. Having said that, the circuit should be designed so the bias current is low enough that it won't destroy parts.
Base resistor method (or) Fixed bias methodBiasing with feedback resistor (or) Collector to base bias methodVoltage divider bias (or) Self bias
biasing resistor is important because the voltage passing through it will limit the current and derive the next device, i.e. transistor etc. when a signal is applied to this circuit, biasing resistor helps to signify that signal and as a result we can examine our output.
The emitter resistor is there to provide DC bias to the base. If it is not bypassed, then the AC output signal is also dropped across this resistor, effectively lowering the output swing. When a bypass capacitor is added, the DC bias still flows through the resistor, but the capacitor acts as a short circuit for the AC signal, so that the AC signal is not reduced. The capacitor selected must be large enough so it appears as a very low resistance at the lowest frequency the amplifier will pass.
of course stability of self bias circuit is much greater than fixed bias circuit
A variable resistor means that the resistance can be varied, usually by using a slide. A fixed resistor can not be varied.
connect the base of the transistor to a variable resistor and to a normal resistor
connect the base of the transistor to a variable resistor and to a normal resistor