amp circuit

Introduction :
In almost all electronics equipments contains amp circuit. In this type of equipments ,there is necessary to rise or increase strength or level of signal which is weak.The importance of amp circuit is very very much in this field .So we can say that it has wide range of application .Amp circuit are used in order to amplifying weak electrical signals.
The transistor are widely used in many places such as scientific ,medical ,communication field etc to produced signal in the micro volt and Milli volt range which is weak level signal .So it should be necessary to increase its level or strength using amp circuit drive required equipments .Amp circuit are classified according to their uses or ranges like below:

• Pre-amp circuit ,
• Voltage-amp circuit and
• Power-amp circuit.

Before the invention of transistor ,vacuum tube ,Mercury arc values etc are used in amp circuit .But now transistor is mostly used in amp circuit.According to the number or stage of transistor used in amp circuit ,it is classified as below:

• Single-stage transistor amp circuit and
• Multi-stage transistor amp circuit .

How amp circuit amplifies?

Now we are discussed about transistor amplifying or analysis of amp circuit.This type of configuration is called common emitter configuration.

This type of amp circuit consists of transistor and its biasing resistors ,which help to amplified the weak a.c signal in sufficient level or strength at the out put of the amp circuit. When weak base a.c signal is given to the base of the transistor as above figure ,then the very large voltage(i.e Bita times or 100 times the base currents) appears across the collector resistor( Ro) ,because of high value of collector resister .So we get very large output voltage .This way the transistor amplifies weak signal.

Practical amp circuit:

This amp circuit is a practical circuits .For the required amplification of weak signal ,various circuits elements and their working principle in the amp circuit .Some important terms of practical amp circuit which are described as following:

Input capacitor(Cin):The practical amp circuit consist of an electrolytic capacitor at the input of the each stage which is connected in base of the each transistor in the case of transistor amp circuit .This is used to allows to pass the a.c signal through it whereas block the d.c biasing signal .

Biasing Resistance circuits :It consists of three resistor (i.e Rb1,Rb2 and RE) which are used to proper biasing and stabilisation circuits .This circuits maintain the proper operating point .If the biasing circuits of amp circuit should not be proper arrangement some portion of the negative-cycle of input signal may be cut off in the collector load or out put .

Coupling capacitor(Cc) :This capacitor is used to couple one stage of amp circuit to the next stage of amp circuit .According to the capacitor function ,it isolates the d.c biasing signal of one stage of amp circuit of the next of amp circuit , But only allows to pass the a.c signal which is applied for amplification . If it is not used in amp circuit whole biasing function is unbalanced due to shouting effect of collector resistor.

Emitter by pass capacitor(CE):This capacitor is used in emitter side for grounded it .It is used in parallel with emitter resistor and provided a low resistance path or way, to the high frequency signal or amplified a.c signal .The amplified signal is flowing via collector resistor (Rc) as a result voltage drop across it which reduce the output voltage ,i f we not used it in amp circuit.