CN103926966B - Low Voltage Bandgap Reference Circuit - Google Patents

Abstract

The invention discloses a low-voltage band-gap reference circuit. The low-voltage band-gap reference circuit comprises a first portion and a second portion, wherein the first portion comprises a band-gap reference circuit body consisting of a first starting circuit and two symmetric amplifiers; the output ends of the amplifiers are fed back to an input end through a current mirror structure; required part of current is provided for the amplifiers; grids of two input tubes of the amplifiers are forcedly equal to each other by using the band-gap reference circuit body through BJT (bipolar junction transistors) of two PNP (precision navigation processors), so that a positive temperature coefficient voltage [PTAT (proportional to absolute temperature) voltage] is generated, a current source is provided for the circuit, and moreover, the grid of one of the amplifiers provides inputted PTAT bias voltage for the second portion via a divider resistor; the second portion comprises a band-gap reference circuit body consisting of a second starting circuit and six cascaded OVF (over frequency) circuits; the input end and the output end of each OVF circuit are connected together to form negative feedback; and the output end of the band-gap reference circuit body is connected with a unit gain buffer. The band-gap reference circuit can run in low voltage, and the stability of outputted voltage is high.

Description

Low Voltage Bandgap Reference Circuit

technical field

The invention relates to a bandgap reference circuit (BGR), in particular to a low-voltage bandgap reference circuit.

Background technique

The reference source is an important part of an integrated circuit, and it is widely used in power management chips, temperature sensors, ADCs, DACs, and memories. Because the bandgap reference source is fully compatible with the standard CMOS process, and the accuracy is less affected by the process, it can still work well under low power supply voltage, and the technical indicators of the bandgap voltage reference are excellent, such as: temperature drift Coefficient, power supply rejection ratio, noise, linear adjustment rate, etc. can fully meet the requirements of use. Based on the above advantages, the bandgap reference circuit has been widely used in recent years and has become a research hotspot.

Since the output of the traditional bandgap reference is about 1.2V, the power supply voltage of this reference circuit must be above 1.2V, which limits the application of the bandgap reference under low voltage conditions. With the development of integrated circuit technology, the feature size is getting smaller and smaller, the integration of chips is getting higher and higher, and the power supply voltage is getting lower and lower. Therefore, it is of great significance to study the bandgap reference circuit working under low voltage conditions.

In the prior art, "A CMOS Bandgap Reference Circuit With Sub-1-V Operation" ("A CMOS Bandgap Reference Circuit With Sub-1-V Operation") published in Volume 34 of IEEE Magazine Solid Circuits in May 1999, the paper A classic structure of a bandgap reference voltage source under extremely low power supply voltage is disclosed, and the structure of the bandgap reference voltage source is shown in FIG. 1 . This circuit uses the reference source in the current summation mode. The core idea is to obtain two currents with positive and negative temperature coefficients respectively, and then sum the two currents to obtain the output of the reference source through resistor division. The output voltage of the source can be achieved by adjusting the ratio of the voltage divider resistors.

There are at least the following disadvantages in the above-mentioned prior art:

Although this circuit works under low voltage conditions, because it uses a 2-stage op amp, its speed and frequency are poorer, and its output uses a single-ended output. Compared with the fully differential method, its output voltage swing is smaller , the common mode noise rejection ability is also weaker. The working voltage range of the bandgap reference is not very large, and the circuit stability and radiation resistance are not high.

Contents of the invention

The object of the present invention is to provide a bandgap reference circuit capable of achieving high stability under low voltage conditions.

The purpose of the present invention is achieved through the following technical solutions:

The low-voltage bandgap reference circuit of the present invention includes a first part and a second part;

The first part includes a bandgap reference composed of a first start-up circuit and two symmetrical amplifiers. The output of the amplifier is fed back to the input terminal through a current mirror structure to provide the required part of the current for the amplifier. The bandgap The reference uses two PNP BJTs to force the gates of the two input tubes of the amplifier to be equal, thereby generating a positive temperature coefficient voltage (PTAT voltage), which provides a current source for this circuit, and at the same time divides the gate of one of the amplifiers. The piezoresistor provides the input PTAT bias voltage for the second part;

The second part includes a bandgap reference composed of a second start-up circuit and 6 cascaded OVF circuits, the input and output terminals of each OVF circuit are connected together to form negative feedback, and the output terminal of the bandgap reference connected to a unity-gain buffer.

It can be seen from the above-mentioned technical solution provided by the present invention that the low-voltage bandgap reference circuit provided by the embodiment of the present invention uses a two-layer bandgap reference structure to form a cascaded bandgap, thereby improving the stability of the bandgap reference and reducing the input Bias voltage, thus realizing a bandgap reference circuit with high stability under low voltage conditions. At the same time, the bandgap output passes through a unity-gain buffer, improving the accuracy of the output voltage.

Description of drawings

Fig. 1 is a typical structure of a bandgap reference voltage source in the prior art;

2 is a schematic structural diagram of the first part of the low-voltage bandgap reference circuit provided by the embodiment of the present invention;

FIG. 3 is a schematic structural diagram of the second part of the low-voltage bandgap reference circuit provided by the embodiment of the present invention.

Detailed ways

The embodiments of the present invention will be further described in detail below.

The low-voltage bandgap reference circuit of the present invention, its preferred embodiment is:

Including the first part and the second part;

The first part includes a bandgap reference composed of a first start-up circuit and two symmetrical amplifiers. The output of the amplifier is fed back to the input terminal through a current mirror structure to provide the required part of the current for the amplifier. The bandgap The reference uses two PNP BJTs to force the gates of the two input tubes of the amplifier to be equal, thereby generating a positive temperature coefficient voltage (PTAT voltage), which provides a current source for this circuit, and simultaneously connects the gate of one of the amplifiers (left) The pole provides the input PTAT bias voltage for the second part through the voltage dividing resistor;

The second part includes a bandgap reference composed of a second start-up circuit and 6 cascaded OVF circuits, the input and output terminals of each OVF circuit are connected together to form negative feedback, and the output terminal of the bandgap reference connected to a unity-gain buffer.

The amplifier is a fully differential folded cascode amplifier.

The first start-up circuit and the second start-up circuit are respectively connected with NMOS transistors, and the voltage connected to the grid of the NMOS transistors is a high voltage.

The low-voltage bandgap reference circuit of the present invention uses a 2-layer bandgap reference structure to form a cascaded bandgap, improves the stability of the bandgap reference, and reduces the input bias voltage, thereby achieving high stability under low voltage conditions. Bandgap reference circuit. At the same time, the bandgap output passes through a unity-gain buffer, improving the accuracy of the output voltage.

Specific examples:

The low-voltage bandgap reference circuit mainly includes two parts, the first part is shown in Figure 2, and the second part is shown in Figure 3.

The first part is mainly to provide the reference voltage for the PMOS current source in this circuit, and at the same time provide the bias voltage for the second part through the voltage dividing resistor. The second part is to reduce the operating voltage of the bandgap. Cascading the two sections increases the stability of this circuit.

The first part includes a start-up circuit and a bandgap reference composed of two symmetrical amplifiers, the amplifier is a fully differential folded cascode amplifier, and the output passes through a current mirror structure (P10, P11 constitute a set of current mirrors, P15 , P16 constitutes another set of current mirrors) is fed back to the input terminal to provide the required part of the current for the amplifier, and the gates of the two input tubes of the amplifier are forced to be equal through two PNP BJTs (bipolar junction transistors). As a result, a positive temperature coefficient (PTAP) voltage is generated, and the input PTAT bias voltage is provided for the second part through the voltage dividing resistor (R6, R7). The starting circuit of the bandgap reference is simple, and this part is composed of P12, P13, and N4 Bandgap startup circuit.

The second part is composed of six OVF (offset voltage follower compensation follower) circuits cascaded as shown in Figure 3. The input and output terminals of each OVF circuit are connected together to form negative feedback. P18, P19, and N5 constitute the start-up circuit of this part of the bandgap. At the same time, a unity-gain buffer is connected to the output, and the input and output of the buffer are shorted together.

In the above circuit, the voltages connected to the gates of N4 and N5 are the same high voltage, which turns on the NMOS transistor and pulls down the output voltage.

The beneficial effects of the technical solution of the present invention:

(1) The present invention generates a reference voltage by using a two-layer bandgap reference structure to realize a high-stability reference voltage under low-voltage conditions, and the output passes through a unity-gain buffer to improve the accuracy of the output voltage.

(2) The circuit structure of the present invention has better symmetry, which is beneficial to layout design and improves circuit stability and radiation resistance.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technical field can easily conceive of changes or changes within the technical scope disclosed in the present invention. Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (3)

1. A low-voltage bandgap reference circuit, characterized in that it comprises a first part and a second part; The first part includes a first bandgap reference composed of a first start-up circuit and two symmetrical amplifiers. The output of the amplifier is fed back to the input terminal through a current mirror structure to provide the required part of the current for the amplifier. The bandgap reference uses two PNP BJTs to force the gates of the two input tubes of the amplifier to be equal, thereby generating a positive temperature coefficient voltage, which provides a current source for this circuit, and at the same time passes the gate of one of the amplifiers through a voltage divider resistor Provide the input PTAT bias voltage for the second part; The second part includes a second bandgap reference composed of a second start-up circuit and 6 cascaded compensation follower OVF circuits, and the input and output terminals of each compensation follower OVF circuit are connected together to form a negative feedback , the output terminal of the second bandgap reference is connected with a unity gain buffer. 2. The low-voltage bandgap reference circuit according to claim 1, wherein the amplifier is a fully differential folded cascode amplifier. 3. The low-voltage bandgap reference circuit according to claim 1 or 2, characterized in that, NMOS transistors are respectively connected to the first start-up circuit and the second start-up circuit, and the grid connected to the NMOS transistor The voltage is high voltage.