A reference voltage generation circuit

Abstract

The present invention relates to the field of reference voltage sources, and particularly to a reference voltage generation circuit. The present invention proposes a thin-film transistor integrated reference voltage source with strong anti-interference ability, low temperature coefficient, adjustable output voltage, simple production process and low price cost. The reference voltage source mainly consists of four thin-film transistors. Two single-gate thin-film transistors are used as a current mirror to make the currents in two branches equal. The other two thin-film transistors are double-gate thin-film transistors with their drains and gates short-circuited. The gate-source voltages of the two double-gate thin-film transistors are differentiated to obtain an output voltage signal, effectively eliminating the differences of the thin-film transistors themselves caused by process and other factors between the two branches. The reference voltage source composed of double-gate thin-film transistors can utilize the regulation effect of the top gate on the bottom threshold voltage to adjust the magnitude of the output voltage, making the reference voltage circuit more flexible and practical.

Description

Technical Field

[0001] The present invention relates to the field of reference voltage sources, and particularly to a reference voltage generation circuit. Background Art

[0002] As a key module of an integrated circuit chip, a reference voltage source can stably output externally and is widely used in various high-precision circuits, such as high-precision AD and D / A conversion circuits, high-precision integrated operational amplifiers, high-precision voltage comparators, high-precision portable devices, system-on-chip (SOC), etc. For high-precision circuits and systems, accuracy is a very important performance parameter. The bandgap reference voltage source has a simple circuit structure and excellent temperature characteristics, and is favored by integrated circuit designers and widely used in high-precision circuits and systems. There are three common integrated reference voltage sources: PN junction diode reference voltage source, Zener reference voltage source, and bandgap reference voltage source. As Figure 1 shown is a reference voltage source based on a PN junction diode, which is a simple and cost-effective way to obtain a reference voltage source, with a temperature coefficient of 2200 ppm / °C. As Figure 2 shown is a reference voltage source implemented based on a Zener diode. The temperature coefficient of a single Zener diode is 1500 - 5000 ppm / °C, but the Zener reference voltage source has a weak ability to suppress noise and is difficult to be applied to modern integrated circuits. As Figure 3 shown is a bandgap reference voltage source, which cancels the positive and negative temperature coefficients of the voltages of two branches, so that the operational amplifier outputs a reference voltage independent of temperature.

[0003] However, the existing integrated reference voltage sources in the prior art have the following disadvantages:

[0004] 1. PN junction diode reference voltage source: The temperature coefficient is relatively high, and the requirement for the current source in the circuit is relatively high. Once the current source is not an ideal current source, it will inevitably lead to a significant reduction in the accuracy of the reference source, which is not suitable for circuits with high-precision requirements.

[0005] 2. Zener reference voltage source: The temperature drift performance of the Zener diode can be improved by connecting a negative temperature coefficient element in series, but this method will also increase the reference voltage. In addition, the Zener diode has a weak ability to suppress noise and needs to work in a high-voltage circuit system, resulting in poor noise performance of the Zener reference voltage source.

[0006] 3. Bandgap reference voltage source: Resistors need to be added to adjust the voltage division. Large resistors occupy a large area in an integrated circuit, which is not conducive to integration. There is a high-order non-linear variable related to temperature in the base-emitter voltage of the transistor, which is difficult to eliminate, so it is easily affected by temperature and the temperature coefficient is not good enough. Summary of the Invention

[0007] To solve the above problems, the present invention provides a reference voltage generation circuit with strong interference resistance, low temperature coefficient, adjustable output voltage, simple production process and low cost.

[0008] To achieve the above object, the technical solution adopted by the present invention is: a reference voltage generation circuit, including a constant voltage source Vdd, a positive VTG voltage source, a negative VTG voltage source, a first single-gate thin film transistor TFT1, a second single-gate thin film transistor TFT2, a first double-gate thin film transistor TFT3, and a second double-gate thin film transistor TFT4; both the first double-gate thin film transistor TFT3 and the second double-gate thin film transistor TFT4 are provided with a top gate and a back gate; wherein the positive terminal of the constant voltage source Vdd is connected to the drains of the first single-gate thin film transistor TFT1 and the second single-gate thin film transistor TFT2 through two branches, wherein the gates of the first single-gate thin film transistor TFT1 and the second single-gate thin film transistor TFT2 are short-circuited, wherein the source of the first single-gate thin film transistor TFT1 is connected to the drain of the first double-gate thin film transistor TFT3, and the drain of the first single-gate thin film transistor TFT1 is connected to the gate of the first single-gate thin film transistor TFT1; the source of the second single-gate thin film transistor TFT2 is connected to the drain of the second double-gate thin film transistor TFT4; the back gate of the first double-gate thin film transistor TFT3 is short-circuited to its own drain respectively, and the back gate of the second double-gate thin film transistor TFT4 is short-circuited to its own drain respectively; the sources of the first double-gate thin film transistor TFT3 and the second double-gate thin film transistor TFT4 are connected to the negative terminal of the constant voltage source Vdd; the positive VTG voltage source outputs a positive top gate voltage VTG3 to the top gate of the first double-gate thin film transistor TFT3, and the negative VTG voltage source outputs a negative top gate voltage VTG4 to the top gate of the second double-gate thin film transistor TFT4; the difference between the gate-source voltage VGS3 of the first double-gate thin film transistor TFT3 and the gate-source voltage VGS4 of the second double-gate thin film transistor TFT4 is output as the reference voltage Vout; by adjusting the output voltage of the constant voltage source Vdd, the first single-gate thin film transistor TFT1 and the second single-gate thin film transistor TFT2 are both operated in the saturation region; at the same time, by adjusting the positive top gate voltage VTG3 and the negative top gate voltage VTG4, the first double-gate thin film transistor TFT3 and the second double-gate thin film transistor TFT4 are both operated in the sub-threshold region.

[0009] Preferably, the first single-gate thin film transistor TFT1 and the second single-gate thin film transistor TFT2 have the same size, and the active layer materials of both are the same, and the active layer material is one of amorphous silicon, polycrystalline silicon or indium gallium zinc oxide.

[0010] Preferably, the first double-gate thin film transistor TFT3 and the second double-gate thin film transistor TFT4 have the same size, and the active layer materials of both are the same, and the active layer material is one of amorphous silicon, polycrystalline silicon or indium gallium zinc oxide.

[0011] Preferably, the channel shapes of the first double-gate thin film transistor TFT3 and the second double-gate thin film transistor TFT4 are planar channels, π-shaped channels, or 3D fin-shaped channels.

[0012] Preferably, the width-to-length ratios of the first single-gate thin film transistor TFT1 and the second single-gate thin film transistor TFT2 are the same, and the width-to-length ratios of the first double-gate thin film transistor TFT3 and the second double-gate thin film transistor TFT4 are the same, wherein the width-to-length ratio of the first single-gate thin film transistor TFT1 is less than the width-to-length ratio of the first double-gate thin film transistor TFT3.

[0013] The beneficial effects of the present invention are as follows: The present invention provides a thin film transistor integrated reference voltage source with strong anti-interference ability, low temperature coefficient, adjustable output voltage, simple production process, and low price cost. The reference voltage source mainly consists of four thin film transistors. Two single-gate thin film transistors are used as a current mirror to make the currents in two branches equal. The other two thin film transistors are double-gate thin film transistors with their drains and gates short-circuited. The gate-source voltages of the two double-gate thin film transistors are differentiated to obtain an output voltage signal, effectively eliminating the differences of the thin film transistors themselves caused by process and other factors between the two branches; and the reference voltage source composed of double-gate thin film transistors can utilize the regulation effect of the top gate on the bottom threshold voltage to adjust the magnitude of the output voltage, making the reference voltage circuit more flexible and practical. Description of the Drawings

[0014] Figure 1 is a circuit diagram of a diode voltage division reference in the prior art.

[0015] Figure 2 is a structural circuit diagram of a Zener sharp turn voltage source in the prior art.

[0016] Figure 3 is a bandgap reference voltage source diagram in the prior art.

[0017] Figure 4 is a thin film transistor reference voltage circuit diagram with the power supply of the present application being a constant voltage source.

[0018] Figure 5 is a TCAD hybrid circuit simulation result diagram of a thin film transistor integrated reference voltage circuit.

[0019] Figure 6 is a schematic diagram of a table of the temperature coefficient corresponding to the output voltage of a thin film transistor integrated reference voltage circuit. Detailed Embodiments

[0020] Please refer to Figures 1-6As shown in the figure, the present invention relates to a reference voltage generation circuit, which includes a constant voltage source Vdd, a positive VTG voltage source, a negative VTG voltage source, a first single-gate thin film transistor TFT1, a second single-gate thin film transistor TFT2, a first double-gate thin film transistor TFT3, and a second double-gate thin film transistor TFT4; both the first double-gate thin film transistor TFT3 and the second double-gate thin film transistor TFT4 are provided with a top gate and a back gate; wherein the positive terminal of the constant voltage source Vdd is connected to the drains of the first single-gate thin film transistor TFT1 and the second single-gate thin film transistor TFT2 through two branches, wherein the gates of the first single-gate thin film transistor TFT1 and the second single-gate thin film transistor TFT2 are short-circuited, wherein the source of the first single-gate thin film transistor TFT1 is connected to the drain of the first double-gate thin film transistor TFT3, and the drain of the first single-gate thin film transistor TFT1 is connected to the gate of the first single-gate thin film transistor TFT1; the source of the second single-gate thin film transistor TFT2 is connected to the drain of the second double-gate thin film transistor TFT4; the back gate of the first double-gate thin film transistor TFT3 is short-circuited to its own drain respectively, and the back gate of the second double-gate thin film transistor TFT4 is short-circuited to its own drain respectively; the sources of the first double-gate thin film transistor TFT3 and the second double-gate thin film transistor TFT4 are connected to the negative terminal of the constant voltage source Vdd; the positive VTG voltage source outputs a positive top gate voltage VTG3 to the top gate of the first double-gate thin film transistor TFT3, and the negative VTG voltage source outputs a negative top gate voltage VTG4 to the top gate of the second double-gate thin film transistor TFT4; by adjusting the output voltage of the constant voltage source Vdd, the first single-gate thin film transistor TFT1 and the second single-gate thin film transistor TFT2 both operate in the saturation region; at the same time, by adjusting the positive top gate voltage VTG3 and the negative top gate voltage VTG4, the first double-gate thin film transistor TFT3 and the second double-gate thin film transistor TFT4 operate in the subthreshold region.

[0021] The difference between the gate-source voltage VGS3 of the first double-gate thin film transistor TFT3 and the gate-source voltage VGS4 of the second double-gate thin film transistor TFT4 is then output as the reference voltage.

[0022] Please refer to Figure 4 As shown in the figure, during the process of forming the reference voltage, by adjusting the output voltage of the constant voltage source Vdd, the first single-gate thin film transistor TFT1 and the second single-gate thin film transistor TFT2 both operate in the saturation region; at the same time, by adjusting the positive top gate voltage VTG3 and the negative top gate voltage VTG4, the first double-gate thin film transistor TFT3 and the second double-gate thin film transistor TFT4 operate in the subthreshold region. Figure 4 The final output voltage Vout of the circuit shown is:

[0023]

[0024] Wherein, IDS3 and IDS4 are the currents flowing through the two branches respectively, and VT3 and VT4 are the threshold voltages of the first double-gate thin-film transistor TFT3 and the second double-gate thin-film transistor TFT4 respectively. Therefore, when the currents in the two branches are equal, that is, IDS3 = IDS4, the output voltage Vout is independent of the temperature T:

[0025]

[0026] At this time, the output voltage Vout (reference voltage) can be obtained from the circuit in Figure 4 which is related to the threshold voltages of the first double-gate thin-film transistor TFT3 and the second double-gate thin-film transistor TFT4, and is independent of the ambient temperature.

[0027] When selecting the aspect ratios of the TFTs, TFT1 and TFT2 require small aspect ratios, while TFT3 and TFT4 require large aspect ratios.

[0028] Preferably, the first single-gate thin-film transistor TFT1 and the second single-gate thin-film transistor TFT2 have the same size, and the active layer materials of both are the same, and the active layer material is one of amorphous silicon, polycrystalline silicon or indium gallium zinc oxide.

[0029] Preferably, the first double-gate thin-film transistor TFT3 and the second double-gate thin-film transistor TFT4 have the same size, and the active layer materials of both are the same, and the active layer material is one of amorphous silicon, polycrystalline silicon or indium gallium zinc oxide.

[0030] Preferably, the channel shapes of the first double-gate thin-film transistor TFT3 and the second double-gate thin-film transistor TFT4 are planar channels, π-shaped channels or 3D fin-shaped channels.

[0031] Preferably, the aspect ratios of the first single-gate thin-film transistor TFT1 and the second single-gate thin-film transistor TFT2 are the same, and the aspect ratios of the first double-gate thin-film transistor TFT3 and the second double-gate thin-film transistor TFT4 are the same, and the aspect ratio of the first single-gate thin-film transistor TFT1 is less than the aspect ratio of the first double-gate thin-film transistor TFT3.

[0032] In summary, the beneficial effects of the present application are as follows:

[0033] 1. The reference voltage circuit composed of thin-film transistors has a manufacturing process that is fully compatible with the CMOS process, reducing production costs and improving integration.

[0034] 2. The design of the first double-gate thin-film transistor TFT3 and the second double-gate thin-film transistor TFT4 is adopted, where the difference between the gate-source voltage VGS3 of the first double-gate thin-film transistor TFT3 and the gate-source voltage VGS4 of the second double-gate thin-film transistor TFT4 is output as the reference voltage, and the threshold voltage can be controlled by adjusting the top-gate voltage, thereby controlling the output reference voltage.

[0035] 3. The first single-gate thin-film transistor TFT1 and the second single-gate thin-film transistor TFT2 operate in the saturation region, making the currents in the two branches equal, so that the output reference voltage is less affected by temperature.

[0036] 4. The thin-film transistor structure can be of two types: single-gate and double-gate. The thin-film transistor materials can be various materials such as amorphous silicon, polycrystalline silicon, and amorphous indium gallium zinc oxide (IGZO). The channel shape of the double-gate thin-film transistor can be various shapes such as planar channel, π-shaped channel, and 3D fin-shaped channel.

[0037] 5. There are differences in the aspect ratios of the thin-film transistors used. The first single-gate thin-film transistor TFT1 and the second single-gate thin-film transistor TFT2 acting as current mirrors adopt smaller aspect ratios, while the first double-gate thin-film transistor TFT3 and the second double-gate thin-film transistor TFT4 of the main reference circuit adopt larger aspect ratios.

[0038] 6. The present invention provides a design method for a high-performance and low-cost integrated reference voltage generation circuit based on thin-film transistors (TFTs). There are a total of four thin-film transistors in this new type of integrated reference voltage generation circuit. Two of them are in the form of a current mirror to make the currents in the two branches equal. Then, two diode-connected thin-film transistors (Diode-connected TFTs), that is, thin-film transistors with the drain and gate short-circuited, are used to generate two unequal drain voltages, thereby obtaining a voltage independent of temperature and adjustable, with strong anti-interference ability. In addition, the characteristics of the two Diode-connected TFTs operating in the subthreshold region enable the output voltage to change with the threshold voltages of the two Diode-connected TFTs. At the same time, the use of thin-film transistors simplifies the manufacturing process and has a higher integration level, not only reducing the production cost but also being suitable for large-area preparation.

[0039] The above embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A reference voltage generation circuit, characterized in that: It includes a constant voltage source (Vdd), a positive VTG voltage source, a negative VTG voltage source, a first single-gate thin-film transistor (TFT1), a second single-gate thin-film transistor (TFT2), a first double-gate thin-film transistor (TFT3), and a second double-gate thin-film transistor (TFT4); both the first double-gate thin-film transistor (TFT3) and the second double-gate thin-film transistor (TFT4) are provided with a top gate and a back gate. Among them, the positive terminal of the constant voltage source (Vdd) is connected to the drains of the first single-gate thin-film transistor (TFT1) and the second single-gate thin-film transistor (TFT2) through two branches. The gates of the first single-gate thin-film transistor (TFT1) and the second single-gate thin-film transistor (TFT2) are short-circuited. The source of the first single-gate thin-film transistor (TFT1) is connected to the drain of the first double-gate thin-film transistor (TFT3), and the drain of the first single-gate thin-film transistor (TFT1) is connected to the gate of the first single-gate thin-film transistor (TFT1); the source of the second single-gate thin-film transistor (TFT2) is connected to the drain of the second double-gate thin-film transistor (TFT4); the back gate of the first double-gate thin-film transistor (TFT3) is short-circuited to its own drain respectively, and the back gate of the second double-gate thin-film transistor (TFT4) is short-circuited to its own drain respectively; the sources of the first double-gate thin-film transistor (TFT3) and the second double-gate thin-film transistor (TFT4) are connected to the negative terminal of the constant voltage source (Vdd); the positive VTG voltage source outputs a positive top gate voltage (VTG3) to the top gate of the first double-gate thin-film transistor (TFT3), and the negative VTG voltage source outputs a negative top gate voltage (VTG4) to the top gate of the second double-gate thin-film transistor (TFT4); the difference between the gate-source voltage (VGS3) of the first double-gate thin-film transistor (TFT3) and the gate-source voltage (VGS4) of the second double-gate thin-film transistor (TFT4) is output as the reference voltage (Vout); by adjusting the output voltage of the constant voltage source (Vdd), both the first single-gate thin-film transistor (TFT1) and the second single-gate thin-film transistor (TFT2) operate in the saturation region; at the same time, by adjusting the positive top gate voltage (VTG3) and the negative top gate voltage (VTG4), both the first double-gate thin-film transistor (TFT3) and the second double-gate thin-film transistor (TFT4) operate in the subthreshold region.

2. The reference voltage generation circuit according to claim 1, wherein: The first single-gate thin-film transistor (TFT1) and the second single-gate thin-film transistor (TFT2) have the same size and the same active layer material, and the active layer material is one of amorphous silicon, polycrystalline silicon, or indium gallium zinc oxide.

3. A reference voltage generating circuit according to claim 1, characterized in that: The first double-gate thin-film transistor (TFT3) and the second double-gate thin-film transistor (TFT4) have the same size and the same active layer material, and the active layer material is one of amorphous silicon, polycrystalline silicon, or indium gallium zinc oxide.

4. A reference voltage generating circuit according to claim 1 or 3, characterized in that: The channel shapes of the first double-gate thin-film transistor (TFT3) and the second double-gate thin-film transistor (TFT4) are planar channels, π-shaped channels, or 3D fin-shaped channels.

5. A reference voltage generation circuit according to claim 1, wherein: The width-to-length ratios of the first single-gate thin-film transistor (TFT1) and the second single-gate thin-film transistor (TFT2) are the same, and the width-to-length ratios of the first double-gate thin-film transistor (TFT3) and the second double-gate thin-film transistor (TFT4) are the same, where the width-to-length ratio of the first single-gate thin-film transistor (TFT1) is less than that of the first double-gate thin-film transistor (TFT3).

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