Transcript 211Lec08-TransistorsCMOS

CSCE 211 Digital Design
Lecture 8
Transistors
Topics

Review:
 Combinational Circuits
 Decoders
 Multiplexers




Breadboards, LEDs
Components on integrated circuit (ICs)
Transistors
CMOS
Readings 5.4, 5.7
September 29, 2014
Hot Batteries
You should regularly check your batteries “slightly
warm” is OK but hot indicates that your circuit has a
short circuit.
Unplug quickly and check.
1.
2.
3.
–2–
Look for direct lines Vcc to GND.
Remember you need 330 ohm resistors in series with LEDs
and that includes segments of the seven segment display.
Recheck sections of the breadboard.
CSCE 211H Fall 2014
Transistor: Water Flow Model
Water flow in B raises the
plunger so that water can
flow from C to E.
Small flow turns on and
off bigger flow.
Put signal on B, transfer
signal C to E
Reference: http://www.satcure-focus.com/tutor/page4.htm
–3–
CSCE 211H Fall 2014
Transistor Terminology
Conductor – electrons easily passed from one atom to
next (copper every atom has loose electron)
Insulator – electrons tightly tied down to atoms, no flow
Semiconductor – by adding impurities (doping) can be
changed to increase conductivity
Silicon wafer – used for IC circuits
N-type - silicon doped with boron (excess electrons)
P-ype - silicon doped with phosphorous (excess
“holes” lack of electrons)
–4–
CSCE 211H Fall 2014
Transistor
Reference: http://www.intel.com/education/transworks/
–5–
CSCE 211H Fall 2014
Transistor
Reference: http://www.intel.com/education/transworks/
–6–
CSCE 211H Fall 2014
Transistor
Put Positive charge
on gate.
This attracts
electrons into gap.
This allows electrons
to pass freely
through the gap.
Reference: http://www.intel.com/education/transworks/
–7–
CSCE 211H Fall 2014
Transistor
Reference: http://www.intel.com/education/transworks/
–8–
CSCE 211H Fall 2014
Transistor
Take positive charge off
Gate
This stops attracting
electrons.
This shuts off the flow.
Reference: http://www.intel.com/education/transworks/
–9–
CSCE 211H Fall 2014
N channel transitor
– 10 –
CSCE 211H Fall 2014
P channel Transistor
– 11 –
CSCE 211H Fall 2014
CMOS Inverter
– 12 –
CSCE 211H Fall 2014
CMOS NAND
– 13 –
CSCE 211H Fall 2014
What’s This?
– 14 –
CSCE 211H Fall 2014
– 15 –
CSCE 211H Fall 2014
High impedance
High impedance is the state of an output terminal which
is not currently driven by the circuit; neither high nor
low
Like an unconnected wire
It is also known as hi-Z, tri-stated, or floating
– 16 –
http://en.wikipedia.org/wiki/High_impedance
CSCE 211H Fall 2014
Tri-state Buffer
In the tri-state buffer the enable input (B) acts as a
switch
Note if B is enabled then C=A and if B is not enabled
then C = High-impedance
– 17 –
http://en.wikipedia.org/wiki/Three-state_logic
CSCE 211H Fall 2014
Tri-state Buffer Implementation
.
En
A
L
L
L
H
H
L
B
C
D
Q1
Q2
O
U
T
H H
– 18 –
CSCE 211H Fall 2014
Transmission Gates (Fig 3.45)
A is the input; B the output
– 19 –
En
En_L A
0
1
0
0
1
1
1
0
0
1
0
1
B
CSCE 211H Fall 2014
2-to-1 Mux from transmission gates
.
– 20 –
CSCE 211H Fall 2014
– 21 –
CSCE 211H Fall 2014