Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
2000-04-17
2002-02-19
Lam, Tuan T. (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
06348832
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a current generator circuitry and more particularly, to a reference current generator capable of providing a reference current with substantially small temperature dependence by using two kinds of resistance, which have different temperature coefficients.
2. Description of the Prior Art
In an integrated circuit a number of amplifier stages are coupled to a constant dc current generated at one location and reproduced at many other locations for biasing the different transistors in the circuit. A popular circuit building block for accomplishing current reproduction is the current mirror showing in FIG.
1
. It consists of four matched transistors M
1
, and M
2
, M
3
, and M
4
as well as two diodes D
1
, D
2
and one resistor R
1
. The PMOS transistor M
2
, NMOS transistor M
4
and diode D
1
are in series connected and coupled between a voltage supply and a first reference voltage. On the other hand, the PMOS transistor M
1
, NMOS transistor M
3
resistor R
1
and diode D
1
are in series connected in a similar way and coupled between the voltage supply and a second reference voltage. The second reference voltage can optionally the same as the first reference voltage. The gates of the PMOS transistors M
2
and M
1
are connected each other and also connected to a drain of the PMOS transistor M
1
. Moreover, the gates of the NMOS transistors M
3
and M
4
are connected together and also to a drain of the NMOS transistor M
4
so that it ensures NMOS transistor M
4
in the active mode.
The reference current I
ref
generated can be expressed as
I
ref
=(kT/q*In(A
2
/A
1
))/R
1
, (1)
Where k is the Boltzmann's constant, T is absolute temperature, and q is the electric charge, and A
1
and A
2
are the diode areas of D
1
and D
2
, respectively. In the equation (1), the resistance R
1
is inherently temperature dependent and has temperature coefficient Tc. Thus the current I
ref
has a temperature dependent not only on the term kT/q but also on the denominator, the resistance R
1
. While designing a current generator, it is of great vital that the current generator I
ref
is independent from the power supply as well as the temperature variations.
An object of the invention is thus to solve aforementioned issues.
SUMMARY OF THE INVENTION
The current generator circuitry for providing a reference current with small temperature dependence feature is disclosed. The circuitry comprises a first and a second PMOS transistor, a first and a second NMOS transistor, a first and a second diode, as well as a first and a second resistors. The first PMOS transistor, the first NMOS transistor and the first diode are in series connected between a power reference and a potential reference. It flows with a primary current. The second PMOS transistor has a gate terminal connected to a gate of the first PMOS transistor thereto connect to a drain terminal of the second PMOS transistor. Furthermore, the second NMOS transistor has a gate terminal connected to a gate of the first NMOS transistor thereof connecting to a drain terminal of the first NMOS transistor. The second PMOS transistor, the second NMOS transistor, the second diode, the first resistor and the second resistor are in series connected between the power reference and the potential reference to flow a reference current. Worth to note, the first resistor has a small temperature coefficient and the second resistor has a large temperature coefficient so that the average temperature coefficient is close to a critical value, 3.33E-3. As a result the reference current generator has a feature of very small temperature dependence.
REFERENCES:
patent: 4803541 (1989-02-01), Kouda
patent: 5448103 (1995-09-01), de Wit
patent: 5828110 (1998-10-01), Wollesen
patent: 5900773 (1999-05-01), Susak
patent: 6046491 (2000-04-01), Tamagawa
patent: 6104277 (2000-08-01), Iniewski et al.
Baker & Botts LLP
Lam Tuan T.
Nguyen Hiep
Taiwan Semiconductor Manufacturing Co., Inc.
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