Transistor Digital Circuits
Transcript of Transistor Digital Circuits
Transistor Digital Circuits
Controlled switch model
vCT > VCTex; T- (on); iO > 0; vO 0
vCT < VThn; T- (off); iO = 0; vO = VPS
vCT > VThp ; T- (off); iO = 0; vO = VPS
vCT < VCTex; T- (on); iO > 0; vO 0
The Tn and Tp controlled switches are complementary
TpTn
Switching
Transistor
Model
(on) (on)
TpTn
Switching
Transistor
Model
vCT Tn Tp
L (Low) (off) (on)
H (High) (on) (off)
The Tn and Tp controlled switches are complementary
Analog vs. logic signal
analog signal digital signal
Logic 0 false low
Logic 1 true high
0V → logic 05V → logic 1 CMOS logic family
supplied at +5V
Transistors: essential components of every electronic circuit
Integrated transistors - digital integrated circuit
Transistor (T) count
• Intel 4004, 1971, 10µ, 12mm2, 2,300 T
• Pentium 4 Prescott: 2004, 90nm, 143mm2 112,000,000 T
• Core i7 Broadwell-E (10-core), 2016, 14nm, 246mm2, 3,200,000,000 T
• Apple A12 (hexa-core ARM64), 2018, 7nm, 83.27mm2, 6,900,000,000 T
• GC2 IPU, 2018, 16nm, 825mm2, 23,600,000,000 T
- Intelligence Processing Unit (IPU), specifically designed for artificial intelligence (machine learning)
[https://en.wikipedia.org/wiki/Transistor_count]
MOSFET DIGITAL CIRCUITS
➢ Ideal controlled switch model
➢ Implementation with MOSFET
Logic inverter
0V → logic 0 (Low)
VPS → logic 1 (High)
vA Tn vy
0 (off) VPS
VPS (on) 0
logic 0 - 0V
logic 1 - VPS
Tn and R Tp and R
Logic inverter
A
Y
R
Tn
VPS
Logic invertor: MOSFET and R
n -type channel MOSFET
A
Y
R
Tp
VPS
p -type channel MOSFET
Critical analysis of the logic inverter
With Tn and R
Disadvantage elimination:
R as small as possible, ideal R→0;
Critical analysis of the inverter
withTn and R
Solution: replacement of R with a controlled switch
Disadvantage elimination:
R as small as possible, ideal R→0; R as large as possible, ideal R→∞
Two possible solutions:✓ complementary switches
✓ same input
TTLCMOS
✓ complementary inputs
✓ same switch
MOS transitors BJT transitors and R
CMOS Logic Inverter
vGSn=vI
vGSp=vI-VDD
Logic function NAND, NOR
a) What is the truth table?b) What are the states of the switches?c) How can we eliminate the disadvantages due to the presence of R ?
Problems
Logic function NAND, NOR
CMOS NAND
a) What is the truth table?b) What are the states of alltransistors?
Problem
CMOS NAND
CMOS NOR CMOS AND
19
Transfer characteristicof the CMOS inverter
Ideal (input) Real
Noise margins
maxmax
minmin
OLILL
IHOHH
VVNM
VVNM
−=
−=
Voltage levels and
noise margins for
CMOS logic family
supplied at +5V
V1V5.0V5.1 =−=LNM
V1V5.3V5.4 =−=HNM
Logic circuit 1
Logic circuit 2
out in
BJT DIGITAL CIRCUITS
➢ RTL technology
➢ TTL technology
Switching BJT, digital circuitRB resistor to limit the base current
B
Co
B
BECoB
R
v
R
Vvi
7.0−=
−=
Cex
Bsat
ii =
C
PS
C
CEsatPSCex
R
V
R
vVi
2.0−=
−=
T – (off), if vCo< 0.6V
T – (on), if iB > iBsat
Problem
V5;150
;k2;k100
==
==
PS
CB
V
RR
a) What is the state of T if vCo = 0V? What is the vCE value?
b) What is the state of T if vCo = 5V? What is the vCE value?
c) What is the vCo range to keep T off? What about to keep
it in saturation?
d) If 0V => logic 0 and 5V => logic 1, what is the logic
function of the circuit if ]V}[5;0{Cov
Bipolar Digital Circuits
• Inverter RTL Technology
• NOR
a) What is the schematic for the 2-input NAND gate in a RTL technology?b) What is the truth table?c) What are the states of the transistors?
Problem
TTL: Transistor-Transistor Logic
• Logic Inverter
• from technological reasons in TTL integrated circuits the use of only npn type transistors is preferred
• identical transistors but complementary control
vI1, vI2 ?
Standard TTL gate
Voltage levels and noise margins for TTL family
Supply only with 5V
TTL sub-families with improved performances
Schottky transistor Schottky diode: a metal to semiconductor junction, in conduction 0,5V
vBE=0,8V; vBC=0,5V; vCE=0,3V
• Schottky transistor doesn't enter saturation mode
• increases the commutation speed
Simplified structure of a 2-input NAND gate from the Low-power Schottky family
Logic Gates
0 1
1 0
NOT AB
0 0 0
0 1 0
1 0 0
1 1 1
AND
0 0 0
0 1 1
1 0 1
1 1 1
OR
A+B
Logic Gates – cont.
0 0 1
0 1 1
1 0 1
1 1 0
0 0 1
0 1 0
1 0 0
1 1 0
NORNAND
0 0 0
0 1 1
1 0 1
1 1 0
XOR
Analog Switch (AS)
The AS is an electronic circuit that allows or blocks an input signal to pass to the output of the circuit according to a control signal.
vCo - two levels: VCoL<VTh and VCoH>VCTex
vCo=VCoL ; Tn-(off) ; vO=0
vCo=VCoH ; Tn- (exc) ; vO= vI
no power consumption
VThpVThn
Bidirectional AS with two complementary
controlled switches
vCo=VCoL ; AS - (off) ;
vCo=VCoH ; AS - (on) ;
C=0; AS - off; vO=0
C=1; AS - on; vO=vI
IC 4066 –4 transmission gates; supplied at 10V, ron=150Ω
DG400 (Siliconics) ron=20Ω
VCoH=VDD; VCoL=VSS
vI (VSS; VDD)
AS
AS – CMOS implementationbidirectional transffer
Application: three-channel MUX
What is the output voltage in each of the three situations? Justify the answer.
Application: three-channel MUX