HANDSOME
PART I CHAPTER III
DIODES APPLICATIONS –SPECIAL PURPOSE DIODES
OBJECTIVES
3.1 I-V- characteristics of normal and zener diode and measurement of static and dynamic resistance
3.2 I-V characteristics on CRO
3.3 Clipping circuits using diodes
3.4 Clamping circuits using diodes
3.5 Diode as a voltage multiplier
3.6 Diode used as a meter over current protection
INTRODUCTION
SEMICONDUCTORS
Semiconductors are materials which are used to manufacture all electronic and optoelectronic devices, computers components, IC’s (integrated circuits), mems (microelectromecahnical sytems) and even nanodevices (example quantum dot leds’ ) today. They are so widely used because of their special band gap and its related properties. They even differ from conductors and insulators in their electrical and optical properties because of their band gap (Eg) being different than that of conductors and insulators. Now band gap of a material is defined as the energy difference between conduction band and valence band in terms of electron energy. It is a major factor in deciding a material application for e.g. Conductors have no Eg, semiconductors have an Eg of the order of 1ev.
At room temperature, conductors have very high number of charge carriers in conduction band which gives high conductivity whereas for the case of insulators very few electrons reach the conduction band at room temperature. For semiconductors reasonable numbers of charge carriers reach the conduction band. Refer table 1.1. There is a direct relation between intrinsic charge carrier concentration (ni) and conductivities (σ). Since Ge has three orders of ni greater than that of Si therefore its conductivity (σ) is also 3 orders higher. It is to be noted that they are both good conductors at room temperature.
TABLE 3.1
Insulators Semiconductor Si Ge
Conductor
Band Gap (ev) > 5 ev
~ 1.1
~ 0.6
No band gap
Resistivity (ρ)
( Ω cm ) 10 -12
0.02
DIODES APPLICATIONS –SPECIAL PURPOSE DIODES
OBJECTIVES
3.1 I-V- characteristics of normal and zener diode and measurement of static and dynamic resistance
3.2 I-V characteristics on CRO
3.3 Clipping circuits using diodes
3.4 Clamping circuits using diodes
3.5 Diode as a voltage multiplier
3.6 Diode used as a meter over current protection
INTRODUCTION
SEMICONDUCTORS
Semiconductors are materials which are used to manufacture all electronic and optoelectronic devices, computers components, IC’s (integrated circuits), mems (microelectromecahnical sytems) and even nanodevices (example quantum dot leds’ ) today. They are so widely used because of their special band gap and its related properties. They even differ from conductors and insulators in their electrical and optical properties because of their band gap (Eg) being different than that of conductors and insulators. Now band gap of a material is defined as the energy difference between conduction band and valence band in terms of electron energy. It is a major factor in deciding a material application for e.g. Conductors have no Eg, semiconductors have an Eg of the order of 1ev.
At room temperature, conductors have very high number of charge carriers in conduction band which gives high conductivity whereas for the case of insulators very few electrons reach the conduction band at room temperature. For semiconductors reasonable numbers of charge carriers reach the conduction band. Refer table 1.1. There is a direct relation between intrinsic charge carrier concentration (ni) and conductivities (σ). Since Ge has three orders of ni greater than that of Si therefore its conductivity (σ) is also 3 orders higher. It is to be noted that they are both good conductors at room temperature.
TABLE 3.1
Insulators Semiconductor Si Ge
Conductor
Band Gap (ev) > 5 ev
~ 1.1
~ 0.6
No band gap
Resistivity (ρ)
( Ω cm ) 10 -12
0.02