Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Integrated structure
Reexamination Certificate
2001-08-29
2003-01-07
Riley, Shawn (Department: 2838)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Integrated structure
C327S312000
Reexamination Certificate
active
06504424
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates in general to voltage regulators and, more particularly, to low voltage regulators using the threshold voltage of Metal Oxide Semiconductor Field Effect Transistors (MOSFET) to regulate the output potential.
Most, if not all, electronic devices require at least one Direct Current (DC) voltage for proper operation. Many portable electronic devices require two or more levels of DC potential to operate properly, such as Compact Disc (CD) or Moving Picture Experts Group Audio Layer-
3
(MP
3
) format players, for example. Each DC potential is derived from a battery power supply or an Alternating Current (AC) to DC conversion power supply. Multiple voltage regulators, therefore, are employed to generate the various DC potentials required by the CD or MP
3
players. The voltage regulators are referenced to the single battery or AC-DC power supply input, where a separate voltage regulator is required to generate each level of DC potential required by the portable electronic device.
FIG. 1
illustrates prior art regulator
10
utilizing bipolar transistor
14
as the pass element and zener diode
16
as the reference element. In operation, an input voltage is applied to terminal V
in
, which is larger than the breakdown voltage, V
z
, of zener diode
16
. The base terminal potential of transistor
14
is held relatively constant at V
z
, causing transistor
14
to be conductive. The output voltage, V
out
, of prior art regulator
10
is equal to V
z
−V
f
, where V
f
is the emitter-base potential of transistor
14
. Resistor
12
limits the current flow conducted by zener diode
16
when operating at the breakdown voltage V
z
.
Zener diode
16
operates in the reverse biased, breakdown region and as a result, a reverse leakage current is present due to minority carriers being present within the vicinity of the depletion region. Prior art regulator
10
is subsequently used in applications requiring greater than 5 volt regulated output voltages, since the reverse leakage current is minimal in relatively high output voltage ranges. Applications requiring less than 5 volts, however, increases the amount of reverse leakage current conducted by zener diode
16
, which precludes their use in low voltage applications (<5 volts), where leakage current conducted by zener diode
16
is generally in the milliamp (mA) range.
Hence, there is a need for a simple, low voltage reference, exhibiting low current drain, thereby decreasing power dissipation and increasing efficiency.
REFERENCES:
patent: 4267501 (1981-05-01), Smith
patent: 4318040 (1982-03-01), Hilbourne
patent: 4390833 (1983-06-01), Tzeng
patent: 5272399 (1993-12-01), Tihanyi et al.
Fuchs Margaret E.
Heminger David M.
Robb Stephen P.
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