Information Technology Reference
In-Depth Information
2.2
Current Generator
The current generator, is used in the proposed circuit is marked in Fig. 1. In previous
work [4], the supply dependency is high, so to reduce the supply dependency at lower
technology the following circuit is to be shown here. It gives the current, which is
almost insensitive to supply and temperature variations. In Fig. 1 two beta multipliers
generate currents I
1
and I
2
respectively. Now the common terminology in this circuit
is that, when two parallel lines will subtract with different magnitude, then we get a
straight line. So these two currents I
1
and I
2
are applied to a sub-tractor circuit and a
current is generated, which must be supply independent [4].
The output of Beta-Multiplier is given as
2
2
1
1
I
=
1
−
(1)
1
2
μ
C
(
W
/
L
)
R
K
p
ox
1
P
&
2
2
1
1
I
=
N
1
−
(2)
2
2
μ
C
(
W
/
L
)
R
K
p
ox
1
P
Now these current pass through the sub-tractor circuit and the final current is given as
2
2
2
1
1
1
I
=
1
−
−
N
1
−
(3)
S
2
μ
C
(
W
/
L
)
R
K
K
p
ox
P
1
1
The supply insensitive current I
S
has a positive temperature coefficient. So the tem-
perature sensitivity is also compensated by using a simple current subtraction.
2.3
Voltage Generator
The voltage generator is also shown in Fig. 1. It simply consists of four transistors.
The first two transistors work as potential divider. And the next two transistors biased
by I
S
. Here maximum portion of current pass through last two transistors. Here we use
a Active potential divider circuitry instead of passive circuit by using two transistors.
So this improves the overall performance of reference circuit.
The output voltage V
REF
of the circuit is given by
V
=
V
+
V
−
V
(4)
REF
SGM
23
GSM
21
GSM
13
