Bandgap voltage reference circuit without bipolar transistors

Details Bandgap voltage reference circuit without bipolar transistors Bandgap voltage reference circuit without bipolar transistors

1998-11-12

2001-02-06

Cunningham, Terry D. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Specific identifiable device, circuit, or system

With specific source of supply or bias voltage

C323S313000

Reexamination Certificate

active

06184743

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a bandgap voltage reference circuit, and more particularly, to a bandgap voltage reference circuit used in a gallium arsenide (GaAs) based semiconductor chip.
BACKGROUND OF THE INVENTION
Generally, “bandgap” is a term used in physics and its related semiconductor technology. In physics, when the distance between two atoms approaches the equilibrium interatomic spacing of a diamond lattice, energy level splits into two bands. The two bands are separated by a region which designates energies that the electrons in a solid, such as a type of semiconductor material, cannot possess. The region is referred to a forbidden gap, or a bandgap, for this type of semiconductor material. Any change of thermal energy, electron or photon energy may affect the width of a bandgap. For example, any increase in temperature, electron or photon energy will tend to narrow a bandgap, and similarly, any decrease in temperature, electron or photon energy will tend to widen the bandgap. In addition, depending on the types of semiconductor materials, a bandgap can be wide for one type of material but narrow for another type. For example, silicon generally has a much wider bandgap than gallium arsenide (GaAs).
Many semiconductor devices, such as diodes, bipolar transistors, BiCOMs Field Effect Transistors (FETs) etc., have used bandgap characteristics of a particular semiconductor material, such as silicon. In these devices, such as a diode, a positive electrical charge can narrow the bandgap, and a negative electrical charge can widen the bandgap. In a certain operating region of a device or a circuit containing a plurality of these semiconductor devices, a bandgap can be wide enough such that a voltage at one point of the circuit is stable independent of an applied power supply. The stable voltage at that point is often used as a voltage reference, and a circuit used for designing such a stable reference voltage is often referred to as a bandgap voltage reference circuit.
In silicon bipolar, BiCOMs related technologies, a bandgap circuit employing bipolar transistors has been used to provide stable reference voltages for many years in semiconductor industry.
In recent years, gallium arsenide (GaAs) based semiconductor chips have become more and more utilized in semiconductor industry. In such GaAs chips, where bipolar transistors are not an option, it is generally difficult to design a bandgap circuit to provide a reference voltage which is independent of a power supply voltage of the circuit.
Based on the physics characteristics of the semiconductor materials described above, it is generally known that a bandgap voltage reference circuit (or in short, “a bandgap circuit”) can be built from the exponential relation between the voltage and the current in an emitter junction of a bipolar transistor. It is also known that a Field Effect Transistor (FET) GaAs-based transistor exhibits a square-law relation between the voltage and the current. As a result, FET GaAs-based transistors generally do not meet requirements to build a bandgap reference circuit.
FIG. 1
illustrates a conventional bandgap circuit built from bipolar transistors Q
1
-Q
4
. The reference introducing this type of conventional bandgap circuit can be made to an article authored by A. P. Brokaw, published in IEEE Journal of Solid State Circuits, Vol. SC-9, pp. 388-393, December 1974, entitled “A Simple Three-Terminal IC Bandgap Reference”. In this conventional bandgap circuit, the relation of the currents (I) and resistors (R) are as follows:
I
0
=I
1
;
I
2
=I
3
=I
4
;
R
1
=R
2
=R
3
; and
R
5
=R
6
.
In addition, an amplifier, AMP, has two inputs that are connected to nodes n
1
and n
2
, respectively. With appropriate values of the resistors, the amplifier, and the bipolar transistors, the bandgap circuit makes use of the fixed voltage difference between the base and the emitter of the bipolar transistors, which operate at different current densities, to produce a stable output voltage Vout at node n
0
, i.e. the bandgap circuit output Vout or Vn
0
is independent of a power supply voltage Vdd of the amplifier. Thus, the stable Vn
0
is used as a reference voltage.
Accordingly, there is a need for a bandgap circuit built from FET GaAs-based transistors to provide a stable reference voltage which is independent of a power supply voltage of the circuit.
SUMMARY OF THE INVENTION
The present invention relates generally to a bandgap voltage reference circuit, and more particularly, to a bandgap voltage reference circuit used in a gallium arsenide (GaAs) based semiconductor chip.
The present invention provides a GaAs circuit which uses stacked FETs in which the source and drain of each FET are connected together to form a first terminal and the gate forms a second terminal (an FET configured in this manner being referred to herein as a “Schottky diode”) and an amplifier in an arrangement to provide a stable voltage reference independent of a power supply voltage of the circuit.
In one embodiment of the present invention, the GaAs circuit includes a plurality of GaAs FETs arranged as Schottky diodes being connected to a plurality of resistors, wherein the GaAs circuit is arranged such that a voltage output is independent of a voltage input of the circuit.
One aspect of the present invention is that the gate of each Schottky diode, which is a metal, forms a Schottky junction with the source and the drain of the Schottky diode. The gate is the anode, and the source and the drain are tied together to form the cathode. Each Schottky diode exhibits an exponential relation between the current flowing through the Schottky diode and the voltage across the Schottky diode.
Another aspect of the present invention is that the Schottky diodes are stacked in branches which are electrically connected in parallel. In one embodiment, Schottky diodes are stacked in a first branch and a second branch. The first and second branches are electrically connected in parallel to each other between a voltage output node and ground. In the first branch, a first resistor is electrically connected between the voltage output node and a first node. In the second branch, a second resistor is electrically connected between the voltage output node and a second node. An amplifier has a first input electrically connected to the first node, a second input electrically connected to the second node, and an output electrically connected to the voltage output node. The first branch includes a plurality of sub-branches, such as four sub-branches, of Schottky diodes electrically connected in parallel between the first node and the ground. In each sub-branch, a first Schottky diode is electrically connected to the first node at one end and to a sub-first node at the other end, a second Schottky diode is electrically connected to the sub-first node at one end and to a sub-second node at the other end, and a third resistor is electrically connected to the sub-second node at one end and to the ground at the other end. In the second branch, a first Schottky diode is electrically connected to the second node at one end and to a third node at the other end, and a second Schottky diode is electrically connected to the third node at one end and to the ground at the other end.
A further aspect of the present invention is that the current in the first branch and the current in the second branch are the same, and the currents in each sub-branch are the same. Accordingly, the current in each sub-branch is one-fourth (¼) of the current in the second branch. In one embodiment, the first and second resistors have the same resistance, the Schottky diodes of each branch and sub-branch are the same, and the resistors of each sub-branch have the same resistance.
An additional aspect of the invention is that the gain of the amplifier and the values of the Schottky diodes and the resistors can be selected such that the voltage output is stable.
One advantage of the present invention is that it provi

Affiliated with

Also associated with

Rating

Bandgap voltage reference circuit without bipolar transistors does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Bandgap voltage reference circuit without bipolar transistors, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bandgap voltage reference circuit without bipolar transistors will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2572544