Reference current circuit and reference voltage circuit

Details Reference current circuit and reference voltage circuit Reference current circuit and reference voltage circuit

2002-02-08

2003-03-04

Vu, Bao Q. (Department: 2838)

Electricity: power supply or regulation systems

Self-regulating

Using a three or more terminal semiconductive device as the...

C323S907000, C323S314000

Reexamination Certificate

active

06528979

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reference current circuit and a reference voltage circuit. More particularly, the present invention relates to a bipolar or CMOS reference current circuit formed on a semiconductor integrated circuit, adapted to prevent an appearance of an effect of an early voltage, and operated from a low voltage to output a reference current having a positive temperature characteristic, alternatively to a bipolar or CMOS reference current circuit for outputting a reference current having an optional temperature characteristic. Furthermore, the present invention relates to a bipolar or CMOS reference voltage circuit operated from a low voltage to output a low reference voltage having no temperature characteristics.
2. Description of the Prior Art
First, description will be made of a conventional art regarding a reference current circuit. A reference current circuit has conventionally been available, which is adapted to prevent an appearance of an effect of such an early voltage, and output a reference current having a fixed temperature characteristic. Examples are a bipolar reference current circuit described in Japanese Patent Application Laid-Open No. 191629/1984, and a bipolar reference current circuit and a CMOS reference voltage circuit described in Japanese Patent Application Laid-Open No. 200086/1995.
Now, an operation of the conventional bipolar reference current circuit will be described.
FIG. 1
shows the bipolar reference current circuit described in Japanese Patent Application Laid-Open No. 191629/1984, which is generally called a proportional to absolute temperature (PTAT) current source circuit because it outputs a current proportional to a temperature. However, the PTAT current source circuit shown in
FIG. 1
is adapted to prevent an appearance of an effect of an early voltage. It is because collectors of respective transistors Q
5
and Q
6
are connected to bases of respective transistors Q
3
and Q
4
and, by setting currents flowing to the transistors Q
3
and Q
4
equal to each other, base baias voltages of the transistors Q
3
and Q
4
can be set equal to each other, and thus collector voltages of the transistors Q
5
and Q
6
are set equal to each other.
In
FIG. 1
, the transistors Q
2
and Q
3
are set as unit transistors, and an emitter area ratio of a transistor Q
1
is set to be K
1
times (K
1
>1) as large as that of the unit transistor. Here, if base width modulation is ignored, a relation between a collector current I
C
of the transistor and a voltage V
BE
between the base and an emitter is represented by the following equation (1):
I
C
=KI
S
exp(
V
BE
/V
T
)  (1)
In this case, I
S
denotes a saturation current of the unit transistor; and V
T
a thermal voltage, which is represented by V
T
=kT/q. Here, q denotes a unit electron charge; k Boltzmann constant; T absolute temperature; and K an emitter area ratio with respect to the unit transistor.
Assuming that a DC current amplification factor of the transistor is sufficiently near 1, by ignoring a base current, in the bipolar inverse Widlar current mirror circuit, from the equation (1), relations thus established are represented by the following equations:
V
BE1
=V
T
ln{
I
C1
/(
K
1
I
S
)}  (2)
V
BE2
=V
T
ln(
I
C2
/I
S
)  (3)
V
BE2
=V
BE1
+R
1
I
C1
  (4)
Now, by solving the equation (4) from the equation (1), a relation of an input/output current of the bipolar inverse Widlar current mirror circuit is obtained by the following equation (5):
I
C2
=(
I
C1
/K
1
)exp(
R
1
I
C1
/V
T
)  (5)
FIG. 2
shows an input/output characteristic of the bipolar inverse Widlar current mirror.
In this case, the transistor Q
3
drives the transistor Q
4
. The transistor Q
4
constitutes a current mirror circuit having a current mirror ratio of 1:1 with the transistors Q
5
and Q
6
. Since the transistors Q
1
and Q
2
are respectively driven by the transistors Q
5
and Q
6
, the bipolar self-biased inverse Widlar reference current circuit is provided, and a relation is represented by the following equation (6):
I
C2
=I
C1
  (6)
In the bipolar inverse Widlar current mirror circuit, a mirror current I
C2
is exponentially increased with respect to an increase of a reference current I
C1
. Thus, if an operation point is (I
p
=(V
T
/R
1
)ln K
1
=I
C1
=I
C2
), then I
C1
>I
C2
is established with I
p
>I
C1
, and I
C1
<I
C2
is established with I
p
<I
C1
. Accordingly, when Ip+&Dgr;I (&Dgr;I>0) is supplied to the transistors Q
4
to Q
6
, I
C4
=I
C6
=I
C1
=Ip+&Dgr;I is established. However, since I
C2
>I
C5
=Ip+&Dgr;I is established to cause a shortage of current supplied from the transistor Q
5
, the base current of the transistor Q
3
is pulled, and the transistor Q
3
turns off. Thus, a current flowing to the transistor Q
3
is reduced, and currents of the transistors Q
4
to Q
6
are also reduced to return to IP. Conversely, when I
p
−&Dgr;I (&Dgr;I>0) is supplied to the transistors Q
4
to Q
6
, I
C4
=I
C6
=I
C1
=I
p
−&Dgr;I is established. However, since I
C2
<I
C5
=Ip−&Dgr;I is established to cause a current supplied from the transistor Q
5
to be excessive, a current is pushed into the base of the transistor Q
3
, and the transistor Q
3
turns on. Accordingly, a current flowing to the transistor Q
3
is increased, and currents of the transistors Q
4
to Q
6
are also increased to return to I
p
. That is, a negative feedback current loop is constituted, an operation point is uniquely decided with I
C1
>0, realizing a stable operation.
In addition, since the following equation (7) is established,
Δ
⁢
 
⁢
V
BE
=
 
⁢
V
BE2
-
V
BE1
=
V
T
⁢
ln
⁡
(
I
Cl
/
I
S
)
-
V
T
⁢
ln
⁢
{
I
C2
/
(
K
1
⁢
I
S
)
=
 
⁢
V
T
⁢
ln
⁡
(
I
Cl
/
I
C2
)
=
V
T
⁢
ln
⁡
(
K
1
)
=
R
1
⁢
I
Cl
(
7
)
an equation (8) is obtained:
I
C1
=I
C2
=(
V
T
/R
1
)ln(
K
1
)  (8)
Here, K
1
denotes a constant having no temperature characteristics and, as described above, the thermal voltage V
T
is represented by V
T
=kT/q, exhibiting a temperature characteristic of 3333 ppm/° C. Accordingly, if a temperature characteristic of a resistor R
1
is smaller than that of the thermal voltage V
T
, exhibiting a primary characteristic with respect to a temperature, an output current I
0
of the reference current circuit outputted through the current mirror circuit is proportional to the temperature, realizing a PTAT current source circuit. In this case, since currents flowing to the transistors Q
1
to A
3
are all equal to one another, base bias voltages of the transistors Q
2
and Q
3
are also equal to each other. Thus, since collector voltages of the transistors Q
5
and Q
6
are fixed with these base bias voltages of the transistors Q
2
and Q
3
, and equally set, no effects of Early voltages of the transistors Q
1
and Q
2
appear. Since no changes occur in a desired current mirror ratio even if the collector voltages of the transistors Q
5
and Q
6
are changed to cause an appearance of effects of Early voltages, a highly accurate current output having only small changes with respect to fluctuation in a power supply voltage is obtained.
Next, a conventional art regarding a reference voltage circuit will be described. A reference voltage circuit having no temperature characteristics because of cancellation, and adapted to output a reference voltage of 1.2 V or lower has conventionally been available. An example is described in IEEE Journal of Solid-State Circuits, Vol. 32, No. 11, pp.1790 to 1806, November 1997.
First, an operation of this exemplary reference voltage circuit will be described.
FIG. 3
shows the reference voltage circuit described in IEEE Journal of Solid-State Circuits, Vol. 32, No. 11, pp. 1790 to 1806, November 1997. A c

Affiliated with

Also associated with

Rating

Reference current circuit and reference voltage circuit does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Reference current circuit and reference voltage circuit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reference current circuit and reference voltage circuit will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3083864