Transcript Chapter 10 : Diodes

Chapter 10 : Diodes
M3-1: IC Devices
A Portion of the Periodic Table
Single Crystal Silicon
•Reduction of silica (sand) to metallurgical grade silicon (MGS) with
a purity of about 98% (Al,Fe) by heating silica with carbon ;
SiO2(solid)+2C (solid)---Si (solid) +2CO (gas)
•Converting MGS to trichlorosilane (SiHCl3 );
Si(solid)+3HCl(gas) -- SiHCl3 (liquid)+H2 (gas)
•Purification of trichlorosilane by distillation;
•Chemical vapor deposition of silicon from purified SiHCl3 to obtain
electronic grade polysilicon (EGS) which has a very low impurity
level of 1013/cm3.
2 SiHCl3(gas) + 2H2(gas) --2Si(solid) +6HCl
•Czochralski (CZ) crystal growth to obtain single crystal silicon
Moore’s First Law
Moore’s First Law
Different Integration Levels in the IC Industry
Integration level
Time
Number of devices/chip
Small scale
integration (SSI)
1960-1965
2-100
Medium scale integration 1965-1975
(MSI)
100- 10,000
Large scale integration
(LSI)
1975-1985
10,000- 500,000
Very large scale
integration (VLSI)
1985-1995
500,000- 5,000,000
Ultra large scale
integration (ULSI)
1995- present
> 5,000,000
N-type silicon is created by adding valence five
impurities
P-type silicon is created by adding valence
five impurities
Shockley equation
Exercise 10-1
Load-line analysis of diode circuits
Example 10.1 : Load analysis
Example 10-2 : Load line analysis
- Load line is formed to find the operating point
- Current and voltage can be determined once the operating point is
known .
Example 10-4 . Analysis of a Zener-diode regulator with a
load
Find the load voltage vL and source current IS if vSS = 24 V, R= 1.2 kΏ
and RL= 6 kΏ .
Example 10-5 . Analysis by assumed diode states
10-6 Rectifier Circuits (from ac power to dc power)
Half- wave rectifier circuits
 the source voltage – 0.7 V = the output voltage
When the source voltage is negative, diode is reversed- biased, no current flows
through the load .
Battery charging circuit
Current flows when the ac source voltage is higher than the battey
voltage
R is to limit the magnitude of the current .
When ac source voltage is less than the battery voltage, the diode
is reverse biased and the current is 0
The current only flows in the direction that charges the battery .
 To convert an ac voltage into a nearly constant dc voltage
Place a large capacitance across the output terminals.
When the ac source reaches a positive peak, the capacitor is charged to the peak
voltage
IL : average load current; T : period of the ac voltage
A small ripple : due charge and discharge cycle
Vr : peak-to-peak ripple voltage
Full-wave rectifier circuits
Full-wave rectifier circuits
The capacitor discharges for only a half-cycle before being recharged .
Capacitance is only half of that in the half-wave circuit .
C= ILT/2 Vr
 When ac votage >0, current flows through A, load then returns through B.
 When ac voltage <0, current flows through C and D .
Clipper circuits
Clips off any part of the input waveform above 6 V and less than – 9V .
Both diodes are off , therefore no currents flow when the input voltage is
between -9 and 6 V .
vin > 6V, diode A is ON , v0(t) = 6 V , because the diode connects 6V battery to
the output terminals .
 vin <- 9 V, v0(t) = - 9V (diode B connects to the battery).
R is large enough so that the forward diode current is within reasonable bounds
(few milliamps); but small enough for a negligible voltage drop in the reverse
diode current .
Zener diode can substitute the battery (don’t have to change frequently)
Clipper circuits (cont’d)
vin > 6V, diode A is ON , v0(t) = 6 V , because the diode connects 6V battery to the output terminals
.
vin <- 9 V, v0(t) = - 9V (diode B connects to the battery).
Clipper circuits (cont’d)
Another Example
0.6 V forward voltage drop for the diodes
(a) Sketch the transfer characteristic
(b) Sketch the output waveform if vin (t) = 15 sin (ωt)
Another example
0.6 V forward voltage drop
(a) Sketch the transfer characteristic
(b) Sketch the output waveform if vin (t) = 15 sin (ωt)
Example
0.6 V forward voltage drop for the diodes
(a) Sketch the transfer characteristic
Example
0.6 V forward voltage drop for the diodes
(a) Sketch the transfer characteristic