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Transcript 
Lecture 2
ECE 92
Projects in Electrical and Computer
Engineering
Saturday, March 21, 2015
IEEE @ UCSB
0
Transistor
• The transistor is a three-terminal semiconductor device.
• Can control electric current or voltage between two of
•
the terminals.
Used as amplifier or as switch.
Field-Effect Transistors
JFET, MESFET
Depletion-mode
(normally on)
n-ch
Saturday, March 21, 2015
p-ch
MOSFET
Enhancement-mode
(normally off)
n-ch
IEEE @ UCSB
p-ch
Depletion-mode
(normally on)
n-ch
p-ch
1
JFETs
Drain
N-ch JFET
Drain
Gate
Source
Vds
Ids(Vgs,Vds
)
Vgs
Source
ID
Ohmic or
Triode region
Saturation
region
Vgs= 0
Idss
Vgs= Vt + 1.5
Vgs= Vt + 1.0
Increasing
Vgs
Gate
Vgs= Vt + 0.5
Vgs ≤ Vt (cutoff)
Saturday, March 21, 2015
IEEE @ UCSB
Vds
2
MOSFETs
Drain
NMOS
Drain
Gate
Vds
Gate
Ids(Vgs,Vds
)
Vgs
Source
Source
ID
Ohmic or
Triode region
Saturation
region
Vgs= Vt + 1.5
Vgs= Vt + 1.0
Increasing
Vgs
Vgs= Vt + 2.0
Vgs= Vt + 0.5
Vgs ≤ Vt (cutoff)
Saturday, March 21, 2015
IEEE @ UCSB
Vds
3
BJTs
Ib
NPN BJT
Collector
C
B
Ic=βIB
Base
Emitter
E
Ic, , mA
Forward active region
70 μA
8
50 μA
6
40 μA
30 μA
4
20 μA
2
Increasing Ib
60 μA
10 μA
0 μA
Vce,sat
Saturday, March 21, 2015
IEEE @ UCSB
VCE
4
NMOS and PMOS
Saturday, March 21, 2015
IEEE @ UCSB
5
Example
Find W/L and R for the circuit
below assuming kn = 100 μA/V2
(transconductance), Vt = 1 V
(threshold voltage), and rDS =
40 Ω (drain-to-source
resistance).
Saturday, March 21, 2015
IEEE @ UCSB
6
Op-Amps
• Active circuit element designed to perform mathematica
•
operations of addition, subtraction, multiplication,
division, differentiation and integration.
Useful term: gain=amount of amplification produced by
an op-amp. Defined as:
Vo
K=
Vi
Saturday, March 21, 2015
IEEE @ UCSB
7
Op-Amps
Saturday, March 21, 2015
IEEE @ UCSB
8
Op-Amps
Saturday, March 21, 2015
IEEE @ UCSB
9
Example
30 kΩ
60 kΩ
+
Vs1
30 kΩ
Vo
The switch in the following
figure is open. Find v0 in term
of the inputs vs1 and vs2.
Repeat with the switch closed.
60 kΩ
Vs2
Saturday, March 21, 2015
IEEE @ UCSB
10
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