The field-effect transistor (FET) is a three-terminal device used for a variety of applications that match, to a large extent, those of the BJT transistor. Although there are important differences between the two types of devices, there are also many similarities that will be pointed out in the sections to follow. The primary difference between the two types of transistors is the fact that the BJT transistor is a current-controlled device as depicted in Fig.1a, while the JFET transistor is a voltage-controlled device as shown in Fig.1b.

One of our first concerns in the sinusoidal ac analysis of transistor networks is the magnitude of the input signal. It will determine whether small-signal or large-signal techniques should be applied. There are two models commonly used in the small-signal ac analysis of transistor networks: the re model and the hybrid equivalent model.

Late adulthood - period that begins in the 60s and lasts until death .
§ Late adulthood is the time of:
adjusting to retirement.
decreasing strength and health.
new social roles.
reviewing one’s life. 

The transistor is a three-layer semiconductor device consisting of either two n- and one p-type layers of material or two p- and one n-type layers of material. The former is called an npn transistor, while the latter is called a pnp transistor. In Fig. below both biasing potentials have been applied to a pnp transistor, with the resulting majority- and minority-carrier flow indicated.

The label semiconductor itself provides a hint as to its characteristics. The prefix semi-is normally applied to a range of levels midway between two limits. The term conductor is applied to any material that will support a generous flow of charge when a voltage source of limited magnitude is applied across its terminals. An insulator is a material that offers a very low level of conductivity under pressure from an applied voltage source. A semiconductor, therefore, is a material that has a conductivity level some-where between the extremes of an insulator and a conductor

Early adulthood
 begins in late teens/early 20year and lasts through the 30 year. 
Early adulthood is a time of:
 establishing personal and economic independence
 developing a career

Adolescence :  Is a transition period from childhood to adulthood. It is based on childhood experiences
and accomplishments. It begins with the appearance of secondary sex characteristics and ends when
somatic growth is completed and the individual is psychological mature. 
Physical growth:
Weight:

School Age
School-age period is between the age of 6 to 12 years. The child's growth and development is Characterized by gradual growth . 
Physical Development
Weight:
 School–age child gains about 3.8kg/year.

The combinational logic circuit is built from logical gates only. While the sequential logic circuit is mainly built from flip flops in addition to logical gates