<s>
Diode	B-General_Concept
–	I-General_Concept
transistor	I-General_Concept
logic	I-General_Concept
(	O
DTL	B-General_Concept
)	O
is	O
a	O
class	O
of	O
digital	O
circuits	O
that	O
is	O
the	O
direct	O
ancestor	O
of	O
transistor	B-General_Concept
–	I-General_Concept
transistor	I-General_Concept
logic	I-General_Concept
.	O
</s>
<s>
It	O
is	O
called	O
so	O
because	O
the	O
logic	O
gating	O
functions	O
AND	O
and	O
OR	O
are	O
performed	O
by	O
diode	B-General_Concept
logic	I-General_Concept
,	O
while	O
logical	O
inversion	O
(	O
NOT	O
)	O
and	O
amplification	O
(	O
providing	O
signal	O
restoration	O
)	O
is	O
performed	O
by	O
a	O
transistor	B-Application
(	O
in	O
contrast	O
with	O
RTL	O
and	O
TTL	B-General_Concept
)	O
.	O
</s>
<s>
The	O
DTL	B-General_Concept
circuit	O
shown	O
in	O
the	O
first	O
picture	O
consists	O
of	O
three	O
stages	O
:	O
an	O
input	O
diode	B-General_Concept
logic	I-General_Concept
stage	O
(	O
D1	O
,	O
D2	O
and	O
R1	O
)	O
,	O
an	O
intermediate	O
level	O
shifting	O
stage	O
(	O
R3	O
and	O
R4	O
)	O
,	O
and	O
an	O
output	O
common-emitter	O
amplifier	O
stage	O
(	O
Q1	O
and	O
R2	O
)	O
.	O
</s>
<s>
The	O
turned	O
on	O
transistor	B-Application
's	O
collector	O
current	O
will	O
then	O
pull	O
the	O
output	O
Q	O
low	O
(	O
logic	O
0	O
;	O
VCE(sat )	O
,	O
usually	O
less	O
than	O
1	O
volt	O
)	O
.	O
</s>
<s>
Up	O
until	O
1952	O
,	O
IBM	O
manufactured	O
transistors	B-Application
by	O
modifying	O
off-the-shelf	O
germanium	O
diodes	O
,	O
after	O
which	O
they	O
had	O
their	O
own	O
alloy-junction	O
transistor	B-Application
manufacturing	O
plant	O
at	O
Poughkeepsie	O
.	O
</s>
<s>
In	O
the	O
mid	O
1950s	O
,	O
diode	B-General_Concept
logic	I-General_Concept
was	O
used	O
in	O
the	O
IBM	B-Device
608	I-Device
which	O
was	O
the	O
first	O
all-transistorized	O
computer	O
in	O
the	O
world	O
.	O
</s>
<s>
The	O
designers	O
of	O
the	O
1962	O
D-17B	B-Device
guidance	O
computer	O
used	O
diode-resistor	B-General_Concept
logic	I-General_Concept
as	O
much	O
as	O
possible	O
,	O
to	O
minimize	O
the	O
number	O
of	O
transistors	B-Application
used	O
.	O
</s>
<s>
The	O
IBM	O
1401	O
(	O
announced	O
in	O
1959	O
)	O
used	O
DTL	B-General_Concept
circuits	O
similar	O
to	O
the	O
circuit	O
shown	O
in	O
the	O
first	O
picture	O
.	O
</s>
<s>
IBM	O
called	O
the	O
logic	O
"	O
complemented	O
transistor	B-Application
diode	B-General_Concept
logic	I-General_Concept
"	O
(	O
CTDL	O
)	O
.	O
</s>
<s>
NPN	O
based	O
circuits	O
used	O
+6V	O
and	O
-6V	O
and	O
the	O
transistor	B-Application
switched	O
at	O
close	O
to	O
-6V	O
,	O
PNP	O
based	O
circuits	O
used	O
0V	O
and	O
-12V	O
and	O
the	O
transistor	B-Application
switched	O
at	O
close	O
to	O
0V	O
.	O
</s>
<s>
The	O
1401	O
used	O
germanium	O
transistors	B-Application
and	O
diodes	O
in	O
its	O
basic	O
gates	O
.	O
</s>
<s>
The	O
physical	O
packaging	O
used	O
the	O
IBM	B-Device
Standard	I-Device
Modular	I-Device
System	I-Device
.	O
</s>
<s>
In	O
an	O
integrated	O
circuit	O
version	O
of	O
the	O
DTL	B-General_Concept
gate	O
,	O
R3	O
is	O
replaced	O
by	O
two	O
level-shifting	O
diodes	O
connected	O
in	O
series	O
.	O
</s>
<s>
Also	O
the	O
bottom	O
of	O
R4	O
is	O
connected	O
to	O
ground	O
to	O
provide	O
bias	O
current	O
for	O
the	O
diodes	O
and	O
a	O
discharge	O
path	O
for	O
the	O
transistor	B-Application
base	O
.	O
</s>
<s>
In	O
1962	O
,	O
Signetics	O
introduced	O
the	O
SE100-series	O
family	O
,	O
the	O
first	O
high-volume	O
DTL	B-General_Concept
chips	O
.	O
</s>
<s>
It	O
was	O
the	O
most	O
commercially	O
successful	O
DTL	B-General_Concept
family	O
and	O
copied	O
by	O
other	O
IC	O
manufacturers	O
.	O
</s>
<s>
The	O
DTL	B-General_Concept
propagation	O
delay	O
is	O
relatively	O
large	O
.	O
</s>
<s>
When	O
the	O
transistor	B-Application
goes	O
into	O
saturation	O
from	O
all	O
inputs	O
being	O
high	O
,	O
charge	O
is	O
stored	O
in	O
the	O
base	O
region	O
.	O
</s>
<s>
One	O
way	O
to	O
speed	O
up	O
DTL	B-General_Concept
is	O
to	O
add	O
a	O
small	O
"	O
speed-up	O
"	O
capacitor	O
across	O
R3	O
.	O
</s>
<s>
The	O
capacitor	O
helps	O
to	O
turn	O
off	O
the	O
transistor	B-Application
by	O
removing	O
the	O
stored	O
base	O
charge	O
;	O
the	O
capacitor	O
also	O
helps	O
to	O
turn	O
on	O
the	O
transistor	B-Application
by	O
increasing	O
the	O
initial	O
base	O
drive	O
.	O
</s>
<s>
Another	O
way	O
to	O
speed	O
up	O
DTL	B-General_Concept
is	O
to	O
avoid	O
saturating	O
the	O
switching	O
transistor	B-Application
.	O
</s>
<s>
In	O
1964	O
,	O
James	O
R	O
.	O
Biard	O
filed	O
a	O
patent	O
for	O
the	O
Schottky	O
transistor	B-Application
.	O
</s>
<s>
In	O
his	O
patent	O
the	O
Schottky	O
diode	O
prevented	O
the	O
transistor	B-Application
from	O
saturating	O
by	O
minimizing	O
the	O
forward	O
bias	O
on	O
the	O
collector	O
–	O
base	O
transistor	B-Application
junction	O
,	O
thus	O
reducing	O
the	O
minority	O
carrier	O
injection	O
to	O
a	O
negligible	O
amount	O
.	O
</s>
<s>
His	O
patent	O
also	O
showed	O
how	O
the	O
Schottky	O
transistor	B-Application
could	O
be	O
used	O
in	O
DTL	B-General_Concept
circuits	O
and	O
improve	O
the	O
switching	O
speed	O
of	O
other	O
saturated	O
logic	O
designs	O
,	O
such	O
as	O
Schottky-TTL	O
,	O
at	O
a	O
low	O
cost	O
.	O
</s>
<s>
A	O
major	O
advantage	O
over	O
the	O
earlier	O
resistor	O
–	O
transistor	B-Application
logic	O
is	O
increased	O
fan-in	O
.	O
</s>
<s>
Additionally	O
,	O
to	O
increase	O
fan-out	O
,	O
an	O
additional	O
transistor	B-Application
and	O
diode	O
may	O
be	O
used	O
.	O
</s>
