Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
2000-02-02
2001-06-19
Zweizig, Jeffrey (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C327S513000
Reexamination Certificate
active
06249175
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a self-biasing circuit which generates a constant current (a constant voltage) for generating a bias current and a bias voltage of a functional circuit. More particularly, this invention relates to a self-biasing circuit capable of correcting temperature characteristics.
BACKGROUND OF THE INVENTION
FIG. 3
is a circuit diagram that shows a structure of a conventional self-biasing circuit. In this conventional self-biasing circuit, a reference circuit consisting of NPN transistors
1
and
2
generates a potential difference &Dgr; VBE (=VBE
1
−VBE
2
) based on a base-emitter voltage VBE
1
of the transistor
1
and a base-emitter voltage VBE
2
of the transistor
2
, and generates a reference current IREF
1
based on the &Dgr; VBE and a resistor
3
(having a resistance R
3
). A PNP transistor mirror section connected to the transistors
1
and
2
sees to it that a desired reference output current IREFOUT is generated based on the reference current IREF
1
.
Assuming that the mirror ratio of the PNP transistor mirror section is
1
, the reference current IREF
1
is expressed by the following expression.
IREF
1
=&Dgr;
VBE/R
3
=(
VT
×1
nN
)/
R
3
(1)
where VT denotes a thermal voltage, and N denotes a ratio of the areas of emitters of the transistors
1
and
2
, that is, a mirror ratio of the transistors
1
and
2
.
As explained above, the reference current IREF
1
can be set at a free value according to the mirror ratio N of the transistors
1
and
2
, the mirror ratio of the PNP transistor mirror section as a current supply section, and the resistance R
3
of resistor
3
.
Further, the thermal voltage VT in the expression (1) can be given by the following expression.
VT=k×T/q
(2)
where k denotes Boltzmann constant, T denotes absolute temperature, and q denotes amount of charge. is If temperature coefficient of a resistor is neglected because it is very small, the reference current IREF
1
shows positive temperature characteristics from the thermal voltage VT. In other words, the value of reference current IREF
1
increases as the temperature increases, and the value of reference current IREF
1
decreases as the temperature decreases. Accordingly, the self-biasing circuit itself has positive temperature characteristics.
FIGS. 4 and 5
are circuit diagrams that show the structures of other conventional self-biasing circuits. The self-biasing circuit shown in
FIG. 4
corrects the above-described temperature characteristics by adding a band-gap circuit
17
to the self-biasing circuit shown in FIG.
3
. The self-biasing circuit shown in
FIG. 5
corrects the temperature characteristics by adding a circuit
18
having negative temperature characteristics to the self-biasing circuit shown in FIG.
3
. The negative temperature characteristics refers to such characteristics that the current value and the like fall along with an increase in temperature, and the current value and the like increase along with a fall in temperature.
The conventional self-biasing circuit shown in
FIG. 3
, however, has a problem that it cannot correct the temperature characteristics, as this self-biasing circuit does not have means for correcting the temperature characteristics. Further, the conventional self-biasing circuit shown in
FIG. 4
has a problem that it is costlier and it requires a large power consumption, as this self-biasing circuit has a large area and a large circuit current in a temperature characteristics correcting section (a band-gap circuit
17
) for correcting the temperature characteristics. Further, the conventional self-biasing circuit shown in
FIG. 5
has a problem that it is difficult to drive at a low voltage and it requires a large power consumption, as a temperature characteristics correcting section (a circuit
18
) requires a voltage equal to or above 2 VBE (a base-emitter voltage of the transistor) plus Vsat (a saturation voltage of the transistor).
While various performances have been desired in ICs in the communications field in recent years, particularly, there has been strongly desired a reduction in power consumption that determines communication time of a portable telephone and others. Therefore, attentions have been paid to circuits of low-voltage driving and low-power consumption.
SUMMARY OF THE INVENTION
The present invention has been made in light of the problems described above. It is an object of the present invention to provide a self-biasing circuit capable of having desired temperature characteristics by correcting the temperature characteristics while reducing cost and power consumption.
According to one aspect of the present invention, a self-biasing circuit generates a reference current having positive temperature characteristics and a reference current having negative temperature characteristics using the same transistor. Thus, it is possible to correct the temperature characteristics by making a reference current generated that is the sum of the reference currents having positive and negative temperature characteristics by a low-voltage driving and low-current circuit using a simple structure.
According to another aspect of the present invention, a resistor for flowing a reference current having negative temperature characteristics is connected to the base of a transistor for generating a reference current having positive temperature characteristics. Thus, it is possible to correct the temperature characteristics by making a reference current generated that is the sum of the reference currents having positive and negative temperature characteristics by a low-voltage driving and low-current circuit in a simple structure.
According to still another aspect of the present invention, a fifth transistor flows positive and negative reference currents through a first resistor and a second resistor. Thus, it is possible to correct the temperature characteristics by making a reference current generated that is the sum of the reference currents having positive and negative temperature characteristics by a low-voltage driving and low-current circuit in a simple structure.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.
REFERENCES:
patent: 4605892 (1986-08-01), Seevinck et al.
patent: 4792748 (1988-12-01), Thomas et al.
patent: 4882533 (1989-11-01), Kelley
patent: 440316 (1992-04-01), None
patent: 5324108 (1993-12-01), None
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