JPS63133216A - Constant voltage generating circuit - Google Patents

Abstract

PURPOSE:To obtain a constant voltage generating circuit that has its reduce occupying area and also maintains the output voltage stability, by using a constant voltage generating blocks which turn on the prescribed transistors for a slight period of time at an optional number of stages. CONSTITUTION:The power supply voltage VCC applied to power supply terminals 25 and 26 is supplied to the gate of a P-MOSTR 21 via N-MOSTR 27 and 28. Both TR 27 and 28 have working threshold value VN and therefore the gate potential of the TR 21 is set at VCC-2VN. Then 2VN>VP is satisfied when the working threshold value of the TR 21 is set at VP and the difference 2VN-VP is minute. Thus, the TR 21 is slightly turned on to obtain a function equivalent to a high resistance. IN such a constitution, a potential approximately equal to 2VN emerges at the output voltage V1. Thus, the TR 21 has a function equivalent to a high resistance and therefore the output V1 maintains a comparatively stable potential against the fluctuation of the voltage VCC. The output voltage has higher stability when constant voltage blocks 20 and 30 of such constitutions are provided at plural stages.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to reducing the area occupied by a constant voltage generating circuit used in semiconductor integrated circuits and the like.

[Conventional technology]

2. Description of the Related Art Electronic circuits such as semiconductor integrated circuits are often provided with a constant voltage generating circuit that continues to supply a constant voltage even if the power supply voltage fluctuates. FIG. 5 is a circuit diagram showing a conventional example of such a constant voltage generating circuit. In the figure, this constant voltage generating circuit 1 includes a resistor 3 and an N'f-Jannel MOS transistor (hereinafter referred to as rN -MO3TJ) A series connection with 4.5 is inserted. And constant voltage output V. 0. is obtained from between the resistor 3 and N - MOST 4.

Next, the operation of this circuit will be explained. When the power supply voltage VCc is applied to the power supply terminal 2, a current flows from the power supply terminal 2 to the ground level GND through the resistor 3 and the N-MO8 4.5 due to the voltage Vco. Of these, N-M
In the series connection part of O8T4.5, N-MO8T
When the operating threshold value of VN is VN, a voltage drop of approximately (2VN) occurs. Therefore, the power supply voltage V. 0 fluctuates, the output V maintains a substantially constant value (2VN), and most of the fluctuations in the ut power supply voltage KVoo are absorbed by the resistor 3. Therefore, the output V. ut becomes a constant voltage output.

(Problem to be Solved by the Invention) By the way, in order to obtain such a constant voltage output V.ut, the resistance value of the resistor 2 is required to be approximately 1 MΩ. This is due to the fact that the voltage drop between G When the current fluctuates, the fluctuation of the current flowing from the power supply terminal 2 toward the ground level GND also becomes relatively large, and as a result,
The fluctuation of the voltage drop of N-MO8T4.5 increases,
This is because the stability of the output voltage is hindered.

However, in a semiconductor integrated circuit or the like, a considerable area is required to provide such a resistance of 1 MΩ. For example, if you try to obtain a resistance value of 1MΩ with a polysilicon layer with a sheet resistance of 50Ω/hole, 2μ
A polysilicon layer with a line width of m and a length of 40 mm must be formed. For this reason, such a conventional constant voltage generating circuit has a problem in that it occupies a large area.

The present invention was made to solve the above-mentioned problem in the prior art, and an object of the present invention is to provide a constant voltage generating circuit that occupies a small area while maintaining the stability of the output voltage.

[Means for solving problems]

In order to achieve the above object, in the constant voltage generation circuit according to the present invention, a series connection between a predetermined transistor and a first active element circuit having a predetermined operating threshold is connected between a power supply and a ground level. A second active element circuit is inserted between the power supply and the control 11 electrode of the transistor, and has an operation threshold that is the same as or an arbitrary small amount larger than the operation threshold of the transistor. An arbitrary number of stages of constant voltage output blocks are provided which are interposed between the transistors and provide a constant voltage output corresponding to the potential between the transistor and the first active element circuit.

(Operation) The second active element circuit included in the constant voltage generating circuit of the present invention has an operating threshold that is equal to or larger than the operating threshold of the transistor by an arbitrary small value. Therefore, the transistor is slightly turned on by the potential applied to the control electrode of the transistor through this second active element circuit.
This transistor will have the same function as a high resistance element, and the output taken out between this transistor and the first active element circuit will be a constant voltage output.

Since no resistance element is used here, a large occupied area is not required.

By providing an arbitrary number of stages of constant voltage generating blocks configured in this manner, a constant voltage output having desired stability can be obtained.

(Embodiment) FIG. 1 is a circuit diagram showing the configuration of a constant voltage generation circuit which is an embodiment of the present invention. In the figure, this constant voltage generation circuit 10 is configured as a multistage connection of two constant voltage generation blocks 20 and 30. Of these, first, the configuration and operation of the constant voltage generation block 20 on the front stage side will be explained.

This constant voltage generation block 20 has a P-channel MOS transistor (hereinafter referred to as IP-MO8TJ) 21 and N-MO8Ts 22 and 23 connected in series, each of which is diode-connected. This series 1a connection is inserted between the power supply terminal 24 and the ground level GND, and the source of the P-MO8T21 is connected to the power supply terminal 24, and
The sources of the N-MO8T23 are connected to the ground level GND. Therefore, N-MO8T22゜2
3 is the "first circuit" in this invention.
This corresponds to the active element circuit J of . These N-MO8T2
The operating threshold for each of 2.23 is VN.

On the other hand, between the power supply terminals 25 and 26 and the gate of the N-MO8T21, there are two N
-MO8T27.28 is inserted. These N-
MO8T27 and 28 are connected in series with each other, and N-
The gate and drain of MO8T27 are connected to the power supply terminals 25 and 26, respectively, and the source of N-MO8T28 is connected to P.
- connected to the gates of MOST21, respectively. The circuit consisting of this N-MO8T27.28 corresponds to the "second active element circuit" in the present invention.

These N-MO8T27.28 also have the above-mentioned operating threshold vN. This threshold value vN is determined by the diode-connected N-MO8T as illustrated in FIG.
It has a value corresponding to the rising voltage Va at . In addition,
From this constant voltage output block 10, P-MO8-21
The node potential V1 between and N-MO8T22 is taken out as a constant voltage output on the previous stage side.

Next, the operation of this constant voltage generation block 20 will be explained. Power supply voltage V applied to power supply terminals 25 and 26. C
is P-MO3T21 via N-MO8T27.28
However, both N-MO8T27 and N-MO8T27.28 have an operating threshold value VN. Therefore, P −
The gate potential of MOST 21 becomes (V - 2VN) C.

On the other hand, the source potential of P-MO8T21 is V. It is C.

Therefore, a voltage of (2VN) is applied between the source and gate of this P-MO8T21. By the way, if the operating threshold of this P-MO3T21 is ■P, then (2V14)>V.

However, the difference: (2VN)-V.

is minute. Therefore, P-MO8T21 is slightly turned on, and this P-MO8T21 has a function similar to that of a high resistance.

The remaining N-MO8T22 and 23 correspond to N-MO3T4 and 5 in the conventional circuit shown in FIG. Therefore, for these N-MO8 22.23, approximately (2VN)
This causes a voltage drop of approximately 2N, so that a potential approximately equal to (2N) appears at the output JV1. In this operation, since the P-MO8T21 performs a function equivalent to a high resistance, this output v1 is equal to the power supply voltage V. Maintains a relatively stable potential against zero fluctuations.

However, as will be shown later as a simulation result, the stability of the output voltage is improved by providing multiple stages of constant voltage generation blocks rather than outputting the potential v1, which is the output of the constant voltage generation block 20, as a constant voltage. do. For this reason, in the constant voltage circuit 10 of FIG. 1, two constant voltage generation blocks 20.degree. 30 are connected in multiple stages.

The subsequent constant voltage generation block 30 provided for this reason has almost the same configuration as the constant voltage generation block 20 described above, and P-MO8T31 is replaced by P-MO8T2.
1, ■N-MO8T32゜33.37.38 is N=M
They correspond to O8T22, 23.27.28, respectively. However, this latter stage constant voltage generation block 30 is
Power supply potential cc is set to P-MO8T31 or N-MO8T37.
Rather than connecting to the constant voltage generation block 20 in the previous stage
The output V1 of is used as a new power supply potential. In other words, the potential v1 stabilized to some extent by the constant voltage generation block 20 in the previous stage is applied to the constant voltage generation block 30 in the subsequent stage.
This further stabilizes the constant voltage output and reduces the constant voltage output to 1.

ut Figure 3 shows the first
It is a graph showing the results of determining the input/output characteristics of the constant voltage generation circuit 10 shown in the figure. As can be seen from FIG. 3, the power supply voltage V. Even when 0 fluctuates greatly, the fluctuation in the potential output from the constant voltage 1f generation block 20 is small. Furthermore, the output V 2 obtained as a result of the multistage connection of the constant voltage generation blocks 20.30 has a very good stability Ou°C.

In the constant voltage generating circuit 10 shown in FIG. 1, a high resistance can be obtained without using a resistive element such as polysilicon, so that the area required for forming the circuit can be significantly reduced. can.

By the way, the present invention is not limited to the above-mentioned embodiment, and for example, the following modifications are also possible.

■ As shown in Figure 4, the constant voltage generation circuit 10 of Figure 1
You can also remove If-MO8T28.38 from. Ko(
1) The threshold value VH of each of ``A 4.t, N-MO81'27.37 is P-MO8T21.
．． The circuit constants are set so that they are slightly larger than the threshold ViV of 31.

■ The operating threshold in the "second active element circuit" is
It may be selected within a range of an arbitrary minute IH equal to or larger than the operating threshold of a transistor used as a substitute for a high resistance element. Therefore, as the "second active element circuit", a circuit in which an arbitrary number of diode-connected N-MO8Ts are connected in series or in parallel may be used.

(2) It is possible to provide an arbitrary number of stages of constant voltage generation blocks, but as the number of stages increases, the stability of the output voltage increases and the magnitude of the voltage that can be taken out decreases. For this reason,
It is desirable that the number of stages of constant voltage generation blocks is determined as appropriate depending on the application of the constant voltage circuit.

■ In the above embodiment, an N-MO3T diode connection was used because it was considered to be formed on an MO8 semiconductor integrated circuit, but the first and second An active element circuit may also be formed.

〔Effect of the invention〕

As explained above, according to the present invention, by configuring a predetermined transistor to turn on slightly, this transistor has the same function as a high-resistance element, thereby allowing a high-resistance element such as polysilicon to Since this is not necessary, it is possible to obtain a constant voltage generation circuit that occupies a small area while maintaining the stability of the output voltage.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a constant voltage generation circuit that is an embodiment of this invention, Figure 2 is a characteristic diagram of a diode-connected transistor, and Figure 3 is a simulation analysis of the input/output characteristics of the circuit of the embodiment. A graph showing the results, FIG. 4 is a circuit diagram showing a modification of the present invention, and FIG. 5 is a circuit diagram showing an example of a conventional constant voltage generating circuit. In the figure, 1 and 10 are constant voltage generation circuits, 20° and 30 are constant voltage generation blocks, Voo is a power supply voltage, and vout is a constant voltage output. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A series connection between a predetermined transistor and a first active element circuit having a predetermined operating threshold is inserted between a power supply and a ground level, and the operating threshold is equal to or equal to the operating threshold of the transistor. A second active element circuit having an operating threshold value larger than this by an arbitrary infinitesimal amount is interposed between the power supply and the control electrode of the transistor, and a second active element circuit is inserted between the power supply and the control electrode of the transistor to 1. A constant voltage generation circuit comprising an arbitrary number of stages of constant voltage output blocks that provide an output according to a potential between them as a constant voltage output. (2) A plurality of stages of constant voltage output blocks are provided, and the constant voltage output of the constant voltage output block at the previous stage is used as a power source for the constant voltage output block at the rear stage. The constant voltage generating circuit described in item 1.