Simple reference source circuit without operational amplifier

Abstract

The invention relates to a simple operational-amplifier-free reference source, which is characterized in that a reference source generating circuit comprises a starting circuit consisting of a triode current mirror for providing current bias, and a non-operational-amplifier self-bias circuit consisting of a PMOS (P-channel Metal Oxide Semiconductor) and an NMOS (N-channel Metal Oxide Semiconductor), the band-gap reference circuit is composed of a triode delta VBE with a positive temperature coefficient and a resistor with a negative temperature coefficient, the enable circuit is used for judging whether the reference source works normally or not, and the output circuit is used for outputting current and voltage generated by the band-gap reference circuit. According to the reference source without the operational amplifier, the problems of operational amplifier offset errors, high power supply rejection ratio, anti-interference capability reference voltage precision and reference minimum working voltage are solved; the circuit has the advantages of being small in occupied layout area, high in precision, high in power supply rejection ratio, high in anti-interference capacity, suitable for the low-voltage field and the like.

Description

Technical Field

[0001] The invention relates to the technical field of analog circuits, in particular to a simple reference source without operational amplifier. Background Art

[0002] In recent years, the demand for managed power chips has been increasing day by day. The reference voltage source is an indispensable and important component of the managed power chip, and its performance will directly affect the feasibility and reliability of the entire system. As an important module in integrated circuits, the bandgap reference source is widely used in a variety of analog and mixed-analog integrated circuits such as low-dropout linear regulators (LDOs), rechargeable battery protection chips, communication circuits, and RF transceivers.

[0003] Whether it is a voltage reference source or a current reference source, they frequently appear in various circuits. Their main determining factor is temperature, and their value and change trend can also be modified relatively accurately. This precise formula relationship between the reference source and temperature can ensure the consistency and reliability of the circuit under various temperature conditions.

[0004] The application conditions of bandgap reference are now more stringent. When the power supply fluctuates, the output of the bandgap reference circuit must show strong suppression ability. In addition, the bandgap voltage reference is required to have strong suppression performance under a wider frequency power supply noise. To improve the power supply rejection ratio of the bandgap voltage reference, the cascode structure can be used to reduce the influence of power supply noise by increasing the output resistance.

[0005] At present, whether in the domestic or international market, most of the traditional bandgap reference circuits adopt a structural design with an op amp. This bandgap reference circuit with an op amp as the core is widely used in various analog circuits because of its mature structure and stable performance. They usually use the high gain characteristics of the operational amplifier to amplify the tiny voltage difference generated by the semiconductor device, thereby providing an accurate and stable voltage or current reference. Using the "virtual short" characteristics of the op amp to clamp the voltage, this circuit often has a higher design complexity, consumes more power, and introduces new noise. In addition, due to the presence of the op amp, an offset voltage is generated, affecting the output accuracy. The bandgap reference circuit without an op amp can well avoid the impact of the offset on it, while also reducing power consumption and reducing the occupied layout area.

[0006] Therefore, it is necessary to design a simple op amp-free reference source circuit that has the advantages of high precision, high power supply rejection ratio, and no offset introduced by op amps. Summary of the invention

[0007] In order to solve the above technical problems, a simple op-amp-free reference source circuit of the present invention comprises a reference source generating circuit and a reference source output circuit; the reference source generating circuit comprises: a start circuit, a transistor current mirror for providing current bias;

[0008] The self-bias circuit without op amp is composed of a current bias independent of power supply composed of several PMOS and several NMOS and is composed of several transistors;

[0009] The bandgap reference circuit is based on the transistor ΔV with a positive temperature coefficient. BE Composed of a resistor with a negative temperature coefficient;

[0010] The reference source output circuit includes: an enabling circuit for determining whether the reference source is working normally;

[0011] Output circuit, current bias generated by bandgap reference circuit, reference voltage corrected by trimming circuit.

[0012] In one embodiment of the present invention, the start-up circuit includes a transistor current mirror composed of a group of diode-connected transistors Q0 connected to the base of one or more transistors Q1. When the PN junction voltage between the base of the transistor Q0 and the transmitter reaches the PN junction start-up voltage, the start-up circuit starts to work and provides a bias current to the op amp-free self-bias circuit, that is, the op amp-free self-bias circuit works normally.

[0013] In one embodiment of the present invention, the op amp-free self-bias circuit is a circuit in which a PMOS tube mp1 and two mirror PMOS tubes mp2 and mp3 are connected to an NMOS tube MN1, a mirror NMOS tube MN4, and a diode-connected NMOS tube MN3 respectively to form a loop that is independent of the power supply, and a feedback circuit is formed together with the mirror NMOS tube MN2 and the bandgap reference circuit, which provides a double layer of protection for the loop stability of a simple op amp-free reference source circuit of the present invention, can be applied to the low-voltage field, and also avoids the input offset of the traditional op amp circuit, improves its power supply rejection ratio and anti-interference ability, and because the number of tubes used is relatively small compared to the traditional op amp circuit, it has the advantages of small layout area and the like.

[0014] In one embodiment of the present invention, the bandgap reference circuit comprises a set of transistors Q3 and Q4 with a proportional relationship, the base of the transistor Q3 is connected to the transistor Q4 through resistors R6 and R4 in sequence, the emitter of the transistor Q3 is connected to the ground, and the transistor Q4 is connected to the ground through a correction factor (resistor R5), so as to ensure the consistency of the electrical characteristics of the transistors Q3 and Q4, thereby eliminating the temperature sensitivity of the two tubes due to slight differences in process and structure. In order to ensure that the output voltage of the bandgap quasi-voltage is 1.2V and has zero temperature drift characteristics, the base of the transistor Q3 and the collector of the transistor Q4 are respectively connected to two resistors R1 and R2 of the same resistance value, the same type and matched on the layout, and are also connected to the transistor Q2, and a feedback loop is formed here through the NMOS tube NM3 or the NMOS tube MN4, the NMOS tube MN2. The collector of transistor Q4 is also connected to the bases of transistors Q5 and Q6, firstly to match the currents on the base of transistor Q3 and the collector branches of the two transistors, and secondly, the bandgap reference circuit forms a feedback loop through transistor Q5, NMOS tube MN1, NMOS tube MN2, and resistor R2 to ensure the stability of the circuit, so that the circuit can stably output the bandgap reference voltage and bias current.

[0015] In one embodiment of the present invention, the output circuit biases the diode-connected PMOS tube mp5 through the collector current of the transistor Q6 in the bandgap reference circuit, and then provides bias current to other areas of the circuit through the mirror PMOS tube mp6. The current has a certain temperature characteristic. At the same time, the output of the reference voltage in the bandgap reference circuit accurately outputs a reference voltage of 1.2V through correction by the adjustment circuit.

[0016] In one embodiment of the present invention, the bandgap reference circuit is the most important and important component of the circuit, so it is necessary to ensure whether it works normally. Therefore, the output current bias in the bandgap reference circuit is compared with another fixed port (PMOS tube mp4) through a comparator A0. If the bandgap reference circuit works normally, a high or low enable signal EN is output.

[0017] The above technical solution of the present invention has the following advantages over the prior art: the reference source circuit of the present invention solves the problems of operational amplifier offset error, high power supply rejection ratio and anti-interference ability, reference voltage accuracy and reference minimum operating voltage; a simple positive temperature coefficient transistor ΔV is used. BE A bandgap reference circuit that is basically independent of temperature is generated with a resistor with a negative temperature coefficient, and the feedback circuit makes the entire system circuit highly stable, and also avoids the input offset of the traditional operational amplifier circuit. It has the characteristics of relatively small layout area, high precision, high power supply rejection ratio and high anti-interference ability, and is also suitable for low-voltage fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0019] Figure 1 It is a structural block diagram of a simple reference source circuit without operational amplifier of the present invention;

[0020] Figure 2 It is a circuit principle diagram of the simple reference source circuit without operational amplifier of the present invention;

[0021] Figure 3 It is a circuit schematic diagram of a specific embodiment of an enabling circuit in the simple op-amp-free reference source circuit of the present invention;

[0022] Figure 4 It is a circuit schematic diagram of a specific embodiment of the simple op amp-free reference source circuit of the present invention.

[0023] As shown in the figure, S100 is a start-up circuit; S101 is a circuit without op amp self-bias; S102 is a bandgap reference circuit; S103 is a trimming circuit; S104 is an enabling circuit; and S105 is an output circuit. DETAILED DESCRIPTION

[0024] This embodiment provides a simple reference source circuit without an operational amplifier, and its structural block diagram is as follows: Figure 1 The simple op-amp-free reference source circuit includes a reference source generation circuit and a reference source output circuit, and its circuit schematic diagram is shown in FIG. Figure 2 shown.

[0025] Specifically, the reference source generating circuit includes: a start circuit S100 composed of a transistor current mirror providing current bias; a self-bias circuit S101 without an operational amplifier, which is composed of several PMOS and several NMOS current biases that are independent of the power supply and are composed together with several transistors; a bandgap reference circuit S102, which is based on the transistor ΔV BE Composed of a resistor with a negative temperature coefficient.

[0026] Specifically, the reference source output circuit includes: an enabling circuit S104 for determining whether the reference source works normally, and an output circuit S105 composed of a current bias generated by a bandgap reference circuit and a reference voltage corrected by a trimming circuit S103.

[0027] Furthermore, the op amp-free self-bias circuit S101 of the simple op amp-free reference source circuit avoids the input offset of the traditional op amp circuit and improves the power supply rejection ratio. The PMOS tube mp1 and two mirror PMOS tubes mp2 and mp3 are respectively connected to the NMOS tube MN1, the mirror NMOS tube MN4, and the diode-connected NMOS tube MN3 to form a loop that is independent of the power supply. The mirror NMOS tube MN2 and the bandgap reference circuit S102 together form a feedback circuit, which provides a double-layer guarantee for the loop stability of the simple op amp-free reference source circuit of the present invention. Since the number of tubes used is relatively less than that of the traditional op amp circuit, it has the advantages of small layout area.

[0028] Furthermore, in order to eliminate the influence of process or circuit structure on temperature as much as possible, the bandgap reference circuit S102 of the simple op amp-free reference source circuit is provided with a group of transistors Q3 and Q4 with a certain proportional relationship. The base of Q3 is connected to the transistor Q4 through resistors R6 and R4 in sequence, the emitter of the transistor Q3 is connected to the ground, and the transistor Q4 is connected to the ground through a correction factor (resistor R5). In order to ensure that the output voltage of the bandgap quasi-voltage is 1.2V and has zero temperature drift characteristics, the base of the transistor Q3 and the collector of the transistor Q4 are respectively connected to two resistors R1 and R2 of the same resistance value, the same type and matched on the layout, and are also connected to the transistor Q2, and a feedback loop is formed here through the NMOS tube NM3 or the NMOS tube MN4 and the NMOS tube MN2. The collector of transistor Q4 is also connected to the bases of transistors Q5 and Q6, firstly to match the currents on the base of transistor Q3 and the collector branches of the two transistors, and secondly, the bandgap reference circuit S102 forms a feedback loop through transistor Q5, NMOS tube MN1, NMOS tube MN2, and resistor R2 to ensure the stability of the circuit, so that the circuit can stably output the bandgap reference voltage and bias current.

[0029] Further, the ratio of transistors Q3 and Q4 in the bandgap reference circuit S102 of the simple op-amp-free reference source circuit is 1:10 in the present invention, but it can also be corrected to 1:16 or the like by deleting the correction factor resistor R5 or the resistor R4 connected to the base of transistor Q4 according to the process characteristics adopted by the circuit. The number of transistors Q2 and Q5 is also set according to the process characteristics along with the size of transistors Q3, Q4 and current. Resistors R1 and R2 are determined jointly according to the VBE of the transistors in each process and the bandgap reference voltage 1.2V, as well as the required current size in the bandgap reference circuit.

[0030] Furthermore, the enabling circuit of the simple op-amp-free reference source circuit is used to ensure whether the reference source circuit works normally, and is usually implemented by using a comparator A0, wherein the comparator A0 can be a current comparator or a voltage comparator. The present invention provides a cross-coupled current comparator as the core of the enabling circuit, so that an enabling signal EN can be provided to the subsequent circuit more quickly. The specific circuit schematic diagram is shown in FIG. Figure 3 shown.

[0031] Furthermore, the cross-coupled current comparator of the simple op-amp-free reference source circuit is to lead the bias current output by the bandgap reference circuit S102 through the PMOS tube mp7 to three series-connected NMOS tubes MN5, two series-connected NMOS tubes MN6, and two series-connected NMOS tubes MN7, and then MN7 and the mirror PMOS tube mp4 in the feedback circuit jointly determine the gate voltage of the two series-connected NMOS tubes MN8, thereby turning on and off the NMOS tube MN9 to control the high or low level of the enable signal EN output.

[0032] In the present invention, the complete circuit of an embodiment of the simple op-amp-free reference source circuit is as follows: Figure 4 As shown. The present invention provides a simple op-amp-free reference source circuit, including a start-up circuit, a feedback circuit, a bandgap reference circuit and an enable circuit, to achieve reference voltage generation and start-up timing coordination of analog circuits. The present invention has the characteristics of low operating voltage, high precision, low power consumption, small layout area, etc., and has a very wide range of application scenarios in analog circuits.

[0033] The reference source circuit described in this embodiment, wherein low power consumption means that it can be started at a voltage, such as above 1.7 V. Moreover, compared with the reference circuit with an operational amplifier, the present invention can save the current of 2 to 3 branches.

[0034] Specifically, the high precision is that the power supply rejection ratio (PSR) can reach more than 90dB; secondly, the temperature influence is small, with only about 3mV change in the whole temperature range.

[0035] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A simple op amp-free reference source circuit, characterized in that: It includes a reference source generating circuit and a reference source output circuit; The reference source generating circuit includes: a start circuit S100, which is composed of a triode current mirror for providing current bias; The self-bias circuit S101 without an operational amplifier is composed of a current bias that is independent of the power supply and is composed of a plurality of PMOS and a plurality of NMOS and is formed together with a plurality of transistors; The bandgap reference circuit S102 is based on the transistor ΔV with a positive temperature coefficient. BE Composed of a resistor with a negative temperature coefficient; The reference source output circuit includes: an enabling circuit S104, which is used to determine whether the reference source is working normally; The output circuit S105 is the current bias generated by the bandgap reference circuit and the reference voltage corrected by the trimming circuit S103.

2. The reference source circuit according to claim 1, characterized in that: The start-up circuit S100 includes a transistor current mirror composed of a group of diode-connected transistors Q0 connected to the base of one or more transistors Q1. When the PN junction voltage between the base of the transistor Q0 and the transmitter reaches the PN junction start-up voltage, the start-up circuit S100 starts to work and provides a bias current to the op amp-free self-bias circuit S101.

3. The reference source circuit according to claim 1, characterized in that: The op amp-free self-bias circuit S101 comprises a PMOS tube mp1 and two mirror PMOS tubes mp2 and mp3 connected to an NMOS tube MN1, a mirror NMOS tube MN4, and a diode-connected NMOS tube MN3 to form a loop independent of the power supply, and a feedback circuit is formed through the mirror NMOS tube MN2 and the bandgap reference circuit S102.

4. The reference source circuit according to claim 1, characterized in that: The bandgap reference circuit S102 includes a group of transistors Q3 and Q4 having a proportional relationship. The base of the transistor Q3 is connected to the transistor Q4 through resistors R6 and R4 in sequence. The emitter of the transistor Q3 is connected to the ground, and the transistor Q4 is connected to the ground through resistor R5.

5. The reference source circuit according to claim 1, characterized in that: The output circuit S105 biases the diode-connected PMOS transistor mp5 through the collector current of the transistor Q6 in the bandgap reference circuit S102, and then provides bias current to other areas of the circuit through the mirror PMOS transistor mp6.

6. The reference source circuit according to claim 1, characterized in that: The output current bias in the bandgap reference circuit S102 is compared with another PMOS tube mp4 port through a comparator A0. If the bandgap reference circuit S102 works normally, a high or low enable signal EN is output.

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