Electronic digital logic circuitry – Interface – Current driving
Reexamination Certificate
2001-12-18
2002-12-31
Chang, Daniel D. (Department: 2819)
Electronic digital logic circuitry
Interface
Current driving
C326S032000, C327S539000, C323S313000
Reexamination Certificate
active
06501299
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a current mirror type bandgap reference voltage generator, and in particular to an improved current mirror type bandgap reference voltage generator which is suitable for generating a constant reference voltage regardless of variations in temperature and power voltage, by making use of a current mirror having a large output resistance and a large swing width.
2. Description of the Background Art
In general, a reference voltage generator includes a reference voltage generator using a MOS transistor having a threshold voltage, and a bandgap reference voltage generator using a bipolar transistor. A CMOS bandgap reference voltage generator is discussed in IEEE Journal of Solid-State Circuit, Vol. 34, No. 5, May 1999, entitled by ‘A CMOS Bandgap Reference Circuit with Sub-1-V Operation’.
In a conventional reference voltage generator, the reference voltage changes due to variations of a power voltage VDD, a temperature and a threshold voltage of a MOS transistor. Accordingly, when the power voltage VDD, the temperature and the threshold voltage of the MOS transistor are varied, the conventional reference voltage generator is not normally operated, thereby causing a mis-operation.
A conventional bandgap reference voltage generator using a differential amplifier will now be explained with reference to FIG.
1
.
The conventional bandgap reference voltage generator performs a normal operation only when the voltage of a node Va is greater than ‘V
DSAT.MN23
+V
TN.MN22+DSAT.MN22
’ in an actual DRAM process. But, since the voltage of the node Va is smaller than ‘V
DSAT.MN23
+V
TN.MN22+DSAT.MN22
’, the bandgap reference voltage generator cannot be normally operated. Here, ‘V
DSAT.MN23
’ is a drain voltage of an NMOS transistor MN
23
in a saturated region, ‘V
TN.MN22
’ is a threshold voltage of an NMOS transistor MN
22
, and V
DSAT.MN22
is a drain voltage of an NMOS transistor MN
22
in a saturated region.
In addition, the conventional bandgap reference voltage generator using the differential amplifier has a minimum operation voltage VDDmin over 1.4V. Thus, it is not suitable for the DRAM having a low voltage tendency.
Although not illustrated, the conventional reference voltage generator has a disadvantage in that the reference voltage has a variation ratio of 0.44% in a period where the power voltage is 2.5V and the temperature ranges from 20 to 90° C., and has a high variation ratio of 0.91% in a period where the power voltage ranges from 2.25V to 2.75V and the temperature is 25° C. As a result, the conventional reference voltage generator cannot be relied upon to operate stably.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to reduce variations of a reference voltage due to variations of a power voltage, by using a current mirror.
Another object of the present invention is to reduce variations of the reference voltage due to temperature variations, by separately generating a current proportional to an emitter-base voltage and a current proportional to a thermal voltage.
Still another object of the present invention is to reduce a minimum operation voltage of a bandgap reference voltage generator by using a current mirror.
In order to achieve the above-described objects of the invention, there is provided a current mirror type bandgap reference voltage generator. A first current generator generates a first current proportional to a base-emitter voltage. A second current generator generates a second current proportional to a thermal voltage. A reference voltage generator adds the first and second currents, and generates a constant reference voltage regardless of variations in temperature and power voltage. Here, the first current generator includes a first current mirror for receiving the power voltage, generating and outputting the first current to a plurality of output terminals. The second current generator includes a second current mirror for receiving the power voltage, generating and outputting the second current to the plurality of output terminals.
REFERENCES:
patent: 5936392 (1999-08-01), Taylor
Joo Jong Doo
Kim Young Hee
Chang Daniel D.
Hynix / Semiconductor Inc.
Jacobson & Holman PLLC
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