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Semiconductors - Diodes
Basic diode
germanium or doped silicone material
N-doping = add element with more valence electrons (typically phosphorus)
P-doping = add element with fewer valence electrons (typically boron)
i
i
Cu
P
N
anode
Cu
cathode
i=0
i=0
trans-impedance diagram
high current flow when forwad biased
+i
+i
V2
V1
diode
1/R
zero current flow when reverse biased
V2-V1
threshold before starts conducting
diode drop V
+i
V2
four general types of diodes
1) signal (low current, small V drop)
2) power (higher current, higher V drop)
3) Zener
4) light emitting diode (LED)
resistor
V1
V ≈ 0.6V
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Zener diode
+i
same for forward bias
resistor
breakdown voltage VBD when reverse biased
+i
V2
different VBD are available
diode
VBD
V2-V1
V1
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Half wave rectification
VIN
VOUT
R
no current
leakage
VIN
i
Full wave rectification
VIN
i
VOUT
VOUT
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DC power supply
VOUT
ripple
DC
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Voltage regulators
7805
nominal +5V out
7V < VIN < 25V
up to 1.5A
7808, 7810, 7812, 7815, 7824
LM2940 low dropout (LDO) VIN > 5.5V
7805
nominal -5V out
7912, 7915
LD1117V33, LM2937ET-3.3 V
nominal +3.3V out
TC1264-3.0VAB, LP2950ACZ-3.0
78L05
nominal +5V out
nominal +3V out
7V < VIN < 35V
up to 100 mA
78L62, 78L82, 78L09, 78L12, 78L15
MCP1702 LDO 625 mV dropout up to 250 mA
1.2V, 1.5V, 1.8V, 2.5V, 2.8V, 3.0V, 3.3V, 4.0V, 5.0V
VIN
GND
+5V out
7905
TO-220 package
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Semiconductors - Transistors
NPN Bipolar Junction Transistors (BJT)
doped germanium material
C
Cu
collector
N
Cu
B
base
P
C
E
N
NPN transistor
Cu
emitter
B C E
TO-220 package
NPN TIP 29, 31
Note: collector
connected to tab
i CE  h FE i BE
simple template to create transistors with lithography
Cu
N
Cu
P
Cu
N
PNP BJT
C
Cu
P
Cu
B
C
N
E
P
B C E
TO-220 package
Cu
PNP transistor
i CE  h FE i BE
PNP TIP 30, 32
Note: collector
connected to tab
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Collecter driven load with NPN
Vs
diode drop  
M
iBE = (VIN –  ) / RIN
iCE = hFE iBE
iM = iCE =
Vin
C
Rin
B
h FE VIN   
R IN
E
VIN > 
Emitter driven load with NPN
iBE = (VIN – VE – ) / RIN
Vs
iCE = hFE iBE = hFE (VIN – VE – ) / RIN
Vin
C
Rin
B
iM = iCE + iBE = (1 + hFE)(VIN – VE – ) / RIN
E
M
VE = iM RM
iM = (1 + hFE)(VIN – iM RM – ) / RIN
iM 
1  h FE VIN   
R IN  R M 1  h FE 
VIN > iM RM + 
solve for iM
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Darlingtons
C
i CE  h FE i BE
B C E
TO-220 package
NPN TIP 120, 121, 122
Note: collector
connected to tab
ULN2803A octal Darlingtons
ULN2803A
500 mA per channel at 50V collecter driven load
+Vs
1/8 ULN2803A
B
GND
C
COM
M
1C 18
2 2B
2C 17
3 3B
3C 16
4 4B
4C 15
5 5B
5C 14
6 6B
6C 13
7 7B
7C 12
8 8B
8C 11
9 GND
may be used in parallel – 2500 mA total
TTL
1 1B
COM 10
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Opto-isolators
PS-2501 isolators
1
16
2
3
15
14
4
5
6
7
8
13
12
11
10
9
D
external +15V
Arduino +5V
3K
5K
Arduino digital input
external GND
Arduino GND
+
Arduino +5V
1K
5K
Arduino digital input
external GND
+
E
external +5V
Arduino +5V
Arduino GND
external device +15V
1500
isolated test point
Arduino digital output
500
LED
external device GND
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Semiconductors – Field Effect Transistors (FET)
N-channel MOSFET
drain
gate
D
G
source
S
G D S
TO-220 package
Usually use in full saturation as on-off switch
Linear region when VGS > Vth and VDS < ( VGS – Vth )
Saturation when VGS > Vth and VDS ≥ ( VGS – Vth )
P-channel MOSFET
source
gate
drain
IRF44Z
Note: drain
connected to tab

V2 
i D  h  VGS  Vth VDS  DS 
2 

h
2
i D  VGS  Vth  1   VDS  VDS sat 
2
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Solid- state relay (SSR)
DC60S5
1
4
+
-
-
+
2
3
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Semiconductors – Thyristors
Silicon controlled rectifier (SCR)
anode
iC to A = 0
VGC > Vth
iC to A = on
cathode
Cu
anode
P
gate
N
if VGC falls below Vth , iC to A will remain on until iC to A falls below
a holding current threshold
gate
P
Cu
old technology
N
Cu
Triac (triode for alternating current)
current can flow in both directions
A2
VG_A1 > Vth
A1
i = on
VTH may be different for reverse polarity
gate
if VG_A1 falls below Vth , i will remain on until i falls below
a holding current threshold
Solid State Relays with Triacs
STRONGLY RECOMMEND - include snubbers circuits to cut current when OFF
S505
1
4
+
-
-
+
2
3
cathode