JP2552253B2 - Constant voltage circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a constant voltage circuit formed on an integrated circuit.

[0002]

SUMMARY OF THE INVENTION According to the present invention, in a constant voltage circuit formed on an integrated circuit, the output of the constant voltage circuit formed on the integrated circuit is controlled by adding photodetection means so that the integrated circuit is exposed to light. In this case, the absolute value of the output voltage of the constant voltage circuit is prevented from becoming small.

[0003]

2. Description of the Related Art Conventionally, a constant voltage circuit formed on an integrated circuit is usually not considered at all when it is used such that the integrated circuit is exposed to light as shown in FIG. .

[0004]

However, when the bias current of the constant voltage circuit is made extremely small when the usage method such that the integrated circuit is exposed to light is not taken into consideration as in the conventional case, the constant voltage circuit on the integrated circuit is reduced. When exposed to light, the operating point of the circuit moves due to the photo leak current of the transistor or the photo leak current of the diode parasitic on the transistor, the absolute value of the output voltage decreases, and the output of the constant voltage circuit is driven as the power supply. When the circuit exists, there is a problem that the operation of this circuit stops.

The present invention solves such a problem, and its purpose is to prevent the absolute value of the output voltage of the constant voltage circuit from being exposed to light even when the integrated circuit is exposed to light. By making the value equal to or more than the value, it is intended to guarantee the operation of the circuit using the output of the constant voltage circuit as the driving power source even when light is applied.

[0006]

The constant voltage circuit of the present invention comprises:
A constant voltage circuit which comprises a complementary transistor formed on a semiconductor substrate of the first conductivity type, has a reference voltage source and a photodetecting means, and outputs a constant voltage based on a reference voltage output from the reference voltage source. The photodetection means is provided between the drain and the power supply terminal of the reference voltage output transistor formed of the first conductivity type for outputting the reference voltage of the reference voltage source, and is provided from outside the constant voltage circuit. The semiconductor device further includes a photodetecting diode that detects light applied to the voltage circuit and compensates for fluctuations in the operating point of the constant voltage circuit caused by the light, the photodetecting diode being a second conductive member formed on the semiconductor substrate. Type well and a first-conductivity-type photodetection diffusion layer formed on the well, the photodetection diffusion layer being separated from the diffusion layer of the drain of the reference voltage output transistor, or Reference voltage Characterized by comprising formed to extend the diffusion layer of the drain of the power transistor.

[0007]

According to the present invention, when the integrated circuit is illuminated by the signal from the photodetector, the constant voltage generating means is controlled so that the absolute value of the constant voltage output voltage does not become small. To do.

[0008]

EXAMPLE FIG. 1 shows an example of the present invention. 1, 5, 10
Is a depletion type P-channel MOS transistor,
3, 6, 7 are enhancement type P-channel MOS transistors, 2, 4, 8, 9, 11, 12 are enhancement type N-channel MOS transistors, 13, 1
Reference numerals 4 and 15 are photodetection diodes.

The operation of this circuit is such that the reference voltage source composed of 1 to 4 is received by the voltage follower circuit composed of 5 to 12, and a constant voltage output voltage is output between V _{DD and} D. The operation when light is applied to the circuit when the bias current determined by each of the transistors 1, 5, 10 is very small in the circuit will be described below.

When light is applied to this circuit, if the photo-leakage current and the bias current of the photo-detecting diode are on the order of approximately the same value, the 13 photo-detecting diodes connected between point A and V _SS are Light leakage occurs and the potential at point A is pulled to the V _SS side. Similarly, the 15 photodetection diodes connected between V _DD and the B point pull the potential of the B point to the V _DD side, and the 14 photodetection diodes connected to the C point and the V _DD side change the potential of the C point to V _DD. Pull to the _DD side. By such an operation, the potential at the point C approaches the V _DD side as compared to when the light does not reach, and the potential at the point D approaches the V _SS side. Therefore, V _DD -D
The absolute value of the voltage that appears between the
It will take the same or a larger value than when it does not hit. Therefore, when circuits that operate at the voltage V _Reg between V _{DD and} D are connected, these circuits can operate in the same manner as when there is no light.

The photodetector diodes 13, 14 and 15 in FIG. 1 are manufactured by the method shown in FIGS. 2A, 2B, 2C and 2D. 2 (a) is equivalent to a method of creating a diode P to the 13 diodes ^- have a N ⁺ diode ^- P a N ⁺ diffusion layer provided on the WELL.

FIG. 2B shows an example in which a diode parasitic on the transistor 4 is used as a photodetection diode. In this case, the area of the drain of the N-channel transistor 4 is set to be larger than the normally required size (size capable of making the minimum contact) to form the P ⁻ N ⁺ diode.

FIG. 2C shows a method of forming a diode corresponding to 14 or 15. P ⁺ diffusion is provided on the N ⁻ substrate to form a P ⁺ N ⁻ diode.

FIG. 2 (d) is likewise a method of making a diode of 14 or 15. This is N ^{- P} on the substrate - WEL
By making L, a P ^- N ^- diode is formed and used as a photodetection diode. Further, the method of forming the diodes 14 and 15 can also be realized by making the drain area of the transistor 10 larger than the size normally required, as in FIG. 2B.

FIG. 3 shows an example in which the photodetecting diodes 13, 14, 15 are replaced with other elements. For 13, the OFF connection of the N channel enhancement MOS transistor as shown in 13 'can be used, and l4,
For 15, an OFF connection of a P channel enhancement MOS transistor can be used as in 14 '. In this case, when light is applied to each transistor, a light leak current flows through the channel portion and the potential at each point can be pulled in each direction.

[0016]

As described above, the constant voltage circuit of the present invention forms the constant voltage circuit because the light detecting means for controlling the output of the constant voltage circuit is formed on the integrated circuit forming the constant voltage circuit. It is possible to easily form the photodetection means in the same process as the manufacturing process, and it is possible to obtain the photodetection means having the same characteristics as the characteristics of the transistor included in the constant voltage circuit. The present invention comprises a complementary transistor formed on a semiconductor substrate of the first conductivity type,
In a constant voltage circuit having a reference voltage source and a light detection means, and outputting a constant voltage based on the reference voltage output from the reference voltage source, the light detection means outputs the reference voltage of the reference voltage source. The constant voltage is provided between the drain of the reference voltage output transistor formed of the first conductivity type and the power supply terminal, and detects the light applied to the constant voltage circuit from outside the constant voltage circuit to detect the constant voltage by the light. It includes a photo-detecting diode that compensates for fluctuations in the operating point of the circuit, wherein the photo-detecting diode
The well includes a second conductive type formed on the semiconductor substrate and a first conductive type photodetection diffusion layer formed on the well, and the photodetection diffusion layer is a drain of the reference voltage output transistor. Since it is formed so as to be separated from the diffusion layer of the reference voltage or to extend the diffusion layer of the drain of the reference voltage output transistor, the output voltage of the reference voltage source is stabilized even when the constant voltage circuit is exposed to light. Thus, the fluctuation of the operating point of the constant voltage circuit is compensated and the output voltage of the constant voltage circuit can be made constant. Furthermore, by forming the light detection diffusion layer forming the light detection diode by extending the diffusion layer of the drain of the reference voltage output transistor, the area of the diffusion layer can be increased. Therefore, the photosensitivity is improved, and the magnitude of the light leakage current can be adjusted by adjusting the area. Therefore, even when the integrated circuit is used in a manner where it is exposed to light, the operation of the circuit operated by the constant voltage circuit can be stably maintained.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a constant voltage circuit according to the present invention.

FIG. 2A to FIG. 2D are cross-sectional views of photodetector diodes.

FIG. 3A and FIG. 3B are circuit diagrams of off-connected MOS transistors as light detection means.

FIG. 4 is a circuit diagram of a conventional constant voltage circuit.

[Explanation of symbols]

 13, 14, 15 Photo-detecting diodes 13 ', 14' Off-connected MOS transistors

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 27/04

Claims (1)

(57) [Claims] 1. A complementary transistor formed on a semiconductor substrate of a first conductivity type, comprising a reference voltage source and a light detecting means.
And has a constant voltage based on the reference voltage output by the reference voltage source.
In the constant voltage circuit that outputs a voltage, the light detection unit is formed of a first conductivity type that outputs a reference voltage of the reference voltage source.
Drain and power supply terminal of the selected reference voltage output transistor
It is provided between the child and the constant voltage circuit from outside the constant voltage circuit.
The light emitted to the path is detected and the constant voltage circuit of the light is detected by the light.
A photodetection diode for compensating for fluctuations in the operating point is included, and the photodetection diode includes a well of the second conductivity type formed on the semiconductor substrate and a first well formed on the well.
The diffusion layer for photodetection is of a conductive type, and the diffusion layer for photodetection is separated from the diffusion layer of the drain of the reference voltage output transistor or extends the diffusion layer of the drain of the reference voltage output transistor. A constant voltage circuit characterized by being formed by.