JPH0750531A - Constant voltage circuit - Google Patents

Abstract

PURPOSE:To improve the reliability of the constant voltage circuit as a product in which the constant voltage circuit causing an open fault of a starting resistor in the check stage is surely eliminated. CONSTITUTION:A transistor(TR) Q4 is activated by supplying a current to its base through a resistor R2 to operate a constant current circuit 1 comprising TRs Q2-Q4, diodes D1-D4 and a resistor R1. Then a predetermined bias current is supplied to a base of the TR Q1 being a component of an emitter follower circuit from the constant current circuit 1, which provides an output of a constant voltage. Since a parasitic capacitance C1 is in existence between bases of the TRs Q2, Q3 and ground, a transient current In1 may be supplied through the parasitic capacitance C1 and even when the resistor R2 is in an open fault, the constant voltage circuit is operated. On the other hand, a test pad P1 connecting to a positive feedback loop of the constant current circuit 1 of this constant voltage circuit is used to discriminate whether or not the resistor R2 is in an open fault.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant voltage circuit improved in reliability by improving a bias circuit.

[0002]

2. Description of the Related Art A conventional constant voltage circuit, as shown in FIG. 4, for example, includes a transistor Q ₃₁ forming an emitter follower circuit and a constant current circuit 31 in an output stage. The constant current circuit 31 includes transistors Q _{32 to} Q ₃₄ and a diode D _31.
.About.D ₃₄ and resistor R ₃₁ . Transistor Q
_The diode ₃₁ functions as a constant voltage buffer amplifier obtained by the collector current of the transistor Q ₃₃ by the diodes D _{31 to} D ₃₄ .

The transistors Q ₃₂ and Q _{33 form} a current mirror circuit, and this current mirror circuit causes the diode D to generate a current having substantially the same value as the collector current of the transistor Q ₃₄ connected in series with the transistor Q _32.
Positive feedback is provided to the base of the transistor Q ₃₄ through ₃₁ · D ₃₂ . The constant current circuit 31 is activated via the resistor R ₃₂ when the power source (voltage V _CC4 ) rises.

On the other hand, another constant voltage circuit shown in FIG. 5 does not use a constant current circuit in which a positive feedback is applied to a bias circuit like the above constant voltage circuit, and does not use a transistor Q which constitutes an emitter follower circuit. ₄₁ between the collector and the base of which is connected by a resistor R _41. Further, diodes D _{41 to} D ₄₄ are connected in series to the base of the transistor Q ₄₁ .

In this constant voltage circuit, the constant voltage obtained by the resistor R ₄₁ and the diodes D _{41 to} D ₄₄ is output through the transistor Q _{41 which} operates as a buffer amplifier.

[0006]

If the former constant voltage circuit is composed of a monolithic integrated circuit, the resistance R ₃₂ due to dust or the like in the manufacturing process of the integrated circuit.
May be opened. In this case, the transistor Q
A parasitic current C ₃₁ (shown by a broken line in the figure) existing between the base of ₃₂ · Q ₃₃ and the ground causes a transient current I _n31 to flow when the power supply rises sharply. Further, the transistor Q ₃₄ has a base current I _n32 (≈) by a current mirror circuit composed of the transistors Q ₃₂ and Q _33.
The current I _n31 ) is applied.

The direct current amplification factor of the transistor Q ₃₄ is h
If _FE34, transistor Q _32, the transistor Q ₃₄
H _FE44 × I _n32 becomes the collector current is given by.
For this reason, the transistor Q _34, the transistor Q ₃₂ · Q
It is normally biased by a positive feedback loop composed of ₃₃ and diodes D ₃₁ and D ₃₂ . That is, in this case, the constant current circuit 31 is activated regardless of the resistance R ₃₂ .

Here, the inspection of the integrated circuit having the above-mentioned constant voltage circuit is usually carried out using a power supply having a steep rising edge, or in an environment where noise such as power supply noise exists. In this case, even when the open failure of the resistor R ₃₂ for startup, the transistor Q ₃₄ is biased normally as described above. However, when the product is used, it may be used with a power supply having a gentle rise or a power supply without noise. Therefore, there is a problem in that the product in which the opening failure of the resistor R ₃₂ has occurred cannot be removed, and a problem occurs when the product is used.

On the other hand, in the latter constant voltage circuit, the resistance R
_If the resistance value of _{41 is} , for example, 22 kΩ, the transistor Q
₄₁ and diode D ₄₁ to D ₄₄ bias current I _B41 biasing is about 10 when the supply voltage V _CC5 is 5V
The value of 0 μA becomes, for example, about 550 μA when the power supply voltage V _CC5 is 15V. As described above, in the latter constant voltage circuit, there is a problem in that the bias current has a high dependency on the power supply, and the bias current greatly fluctuates with respect to the fluctuation of the power supply voltage.

The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above problems and provide a highly reliable constant voltage circuit.

[0011]

The constant voltage circuit of the present invention comprises:
In order to solve the above problems, a constant voltage circuit formed as a monolithic integrated circuit is characterized by taking the following means.

That is, the constant voltage circuit of the present invention comprises an emitter follower circuit and a constant current circuit having a base current to the emitter follower circuit and having a positive feedback, for example, a current mirror circuit. One part of the positive feedback loop and the power supply are connected via a starting resistor that starts the constant current circuit, and it is checked whether the starting resistor is open at one end of the starting resistor in the positive feedback loop. An inspection pad is provided for this purpose.

Further, another constant voltage circuit of the present invention is such that an emitter follower circuit, a first constant current circuit which supplies a base current to the emitter follower circuit and has an amplifying function, and biases the first constant current circuit. And a second constant current circuit for

[0014]

In the former constant voltage circuit, since the constant current circuit and the power source are connected via the starting resistor, the constant current circuit is started by the starting resistor when the power source rises. The emitter follower circuit is biased by the constant current obtained by the constant current circuit and functions as a buffer amplifier to generate a constant voltage. Further, since the constant current circuit is positively fed back, it is possible to suppress the change in the bias current due to the change in the power supply voltage.

By the way, when the above-mentioned constant current circuit is configured to have a current mirror circuit composed of, for example, two transistors, a parasitic capacitance exists between the base and the substrate (ground potential) of both transistors. Therefore, even if the starting resistor is opened during the manufacture of the constant voltage circuit, the transient voltage flowing through the parasitic capacitance causes the constant voltage circuit to operate when the rise of the power supply voltage is steep.

On the other hand, in the above-mentioned constant voltage circuit, since the inspection pad is provided at one end side of the starting resistance in the positive feedback loop, even if the starting resistance is opened, the starting pad can prevent the starting resistance. It becomes possible to inspect the open state. Therefore, the open state of the starting resistor can be easily found.

Meanwhile, the latter at a constant voltage circuit, the output current I ₂ of the second constant current circuit, A and the amplification factor of the first constant current circuit and an output current respectively, if I _1, I ₁ Since = AI ₂ , I ₁ / A. Further, the bias current of the second constant current circuit is I ₁ / (A ×), where h _FE is the direct current amplification factor of the output transistor of the second constant current circuit.
h _FE ). This current has a power supply dependency because it is supplied from the power supply, but the above amplification factor reduces fluctuations due to fluctuations in the power supply.

[0018]

【Example】

[Embodiment 1] The following description will discuss Embodiment 1 of the present invention with reference to FIG.

The constant voltage circuit according to this embodiment is formed of a monolithic integrated circuit, and as shown in FIG.
Transistor Q that constitutes an emitter follower circuit in the output stage
₁ and a current mirror circuit that supplies a base current to the transistor Q ₁ .

The collector of the transistor Q ₁ is connected to the power supply to which the power supply voltage V _CC1 is applied, and the base is connected to the collector of the transistor Q ₃ constituting the current mirror circuit. The current mirror circuit is a transistor Q
It is composed of ₂ and Q ₃ , and transistor Q ₂ and Q
_{In 3} , the emitters are both connected to the power supply and the bases are both connected to the collector of the transistor Q ₂ .

The collector of the transistor Q ₄ is connected to the collector of the transistor Q ₂ . The emitter of the transistor Q ₄ is connected to the substrate (not shown) of the monolithic integrated circuit via the resistor R ₁ and is grounded. On the other hand, the collector of the transistor Q ₃ is connected to the anode of the diode D ₁ .

[0022] The cathode of the diode D ₁ is connected to the anode of the diode D _2, the cathode of the diode D ₂ anode base and the diode D ₃ of the transistor Q ₄ is connected. Then, the cathode of the diode D ₃ is connected the anode of a diode D _4, the cathode of the diode D ₄ is grounded.

A resistor R ₂ as a starting resistor and a test pad P ₁ as an inspection pad are connected between the base of the transistor Q ₄ and the power supply.

In this constant voltage circuit, the transistors Q ₂ and Q
₃ , transistor Q ₄ , resistor R ₁ and diode D ₁
The constant current circuit 1 is composed of D ₄ to D ₄ . In the constant current circuit 1, thereby positively fed back to the base of the transistor Q ₄ through the transistor Q ₂ · Q ₃ diode D ₁ · D ₂ a current of approximately the same value as the collector current of the transistor Q ₄ in the current mirror circuit by.

In the constant voltage circuit thus constructed, the transistor Q _{4 is connected} through the resistor R ₂ when the power source rises.
It is the base current of the supply, the transistor Q ₄ is operated. As a result, the collector current I _C4 flows through the transistor Q ₄ through the transistor Q ₂ . Then, a current having the same value as this current is positively fed back to the base of the transistor Q ₄ through the transistor Q ₃ and the diodes D ₁ and D ₂ , so that the constant current circuit 1 starts operating. As a result, the transistor Q ₁ operating as a buffer amplifier is supplied with a constant bias current from the constant current circuit 1 at its base and outputs a constant voltage.

By the way, in this constant voltage circuit, the bases of the transistors Q ₂ and Q ₃ and the substrate (ground potential).
In between, that is, between the collector of the transistor Q ₄ and the substrate, there is a junction capacitance (parasitic capacitance) of C ₁ . Therefore, when the integrated circuit portion is inspected in the manufacturing process of the constant voltage circuit in an environment where a power supply having a sharp rise is used, the transient current I _n1 flows through the parasitic capacitance C ₁ . Therefore, the transistors Q ₂ and Q ₃
Further, the current I _n2 having almost the same value as the current I _n1 is supplied as the base current of the transistor Q ₄ through the diodes D ₁ and D ₂ , and the constant voltage circuit operates even when the resistor R ₂ is open.

On the other hand, since the constant voltage circuit has the test pad P ₁ , the resistance R is set by inserting an ammeter between the test pad P ₁ and the ground.
_The current I _P1 flowing through ₂ can be measured. And
The resistance value of the resistor R ₂ by the current I _P1 V can be obtained as _CC1 / I _P1, resistor R ₂ can determine whether an open state.

[Second Embodiment] The second embodiment of the present invention will be described below with reference to FIG.

The constant voltage circuit according to this embodiment is formed of a monolithic integrated circuit, and as shown in FIG.
Transistor Q that constitutes an emitter follower circuit in the output stage
₁₁ and a current mirror circuit that supplies a base current to the transistor Q ₁₁ .

The collector of the transistor Q ₁₁ is connected to the power supply to which the power supply voltage V _CC2 is applied, and the base is connected to the collector of the transistor Q ₁₂ . The transistor Q ₁₂ has an emitter connected to the power supply and a collector connected to the anode of the diode D ₁₁ via the resistor R ₁₁ . The cathode of this diode D ₁₁ has a diode D
_{The 12} anodes are connected and the cathode of the diode D ₁₂ is grounded. Also, the base of the transistor Q ₁₂ is
Transistors Q ₁₃ and Q ₁₄ that compose the current mirror circuit
Connected to the base of.

The transistors Q ₁₃ and Q ₁₄ have their emitters both connected to the power supply and their bases both connected to the transistor Q _13.
Connected to the collector. The collector of the transistor Q _13, the collector of the transistor Q ₁₅ is connected. The emitter of this transistor Q ₁₅ is a resistor R ₁₂ · R.
_Grounded through ₁₃ .

On the other hand, the collector of the transistor Q ₁₄ has
The collector of the transistor Q ₁₆ is connected. This collector is connected to the base of the transistor Q ₁₅ · Q _16. Also, the emitter of the transistor Q ₁₆ has a resistor R
It is connected to the connection point between ₁₂ and the resistor R ₁₃ .

In this constant voltage circuit, the constant current circuit 11 is constituted by the transistors Q _{13 to} Q ₁₆ and the resistor R ₁₂ . In the constant current circuit 11, is substantially the current of the same value is positively fed back to the base of the transistor Q ₁₅ and the collector current of the transistor Q ₁₅ in the current mirror circuit composed of the transistors Q ₁₃ · Q _14.

Further, the constant voltage circuit includes a transistor Q ₁₇
Is equipped with. The transistor Q ₁₇ has a collector connected to the collector of the transistor Q ₁₃ and an emitter connected to the resistor R ₁₂
Is connected to the connection point of the resistor R ₁₃ . The base of the transistor Q ₁₇ is connected to the power supply via the resistor R ₁₄ as a starting resistor and also to the anode of the diode D ₁₃ . The cathode of this diode D ₁₃ is grounded. Further, a test pad P ₁₁ as an inspection pad is connected to the base of the transistor Q ₁₇ .

In the constant voltage circuit constructed as described above, the diode D ₁₃ is turned on at the time of the rise of the power source, so that the current is supplied to the base of the transistor Q ₁₇ through the resistor R ₁₄ . Then, the transistor Q ₁₇ operates by being supplied with the collector current through the transistor Q ₁₃ . At this time, the collector current I _{C1 3} flowing through the transistor Q ₁₃
And the collector current I _C14 flowing in the transistor Q ₁₄ become substantially equal to each other, and the same collector current is supplied to the transistor Q ₁₆ .

Then, the collector current is positively fed back through the transistor Q ₁₅ to start the operation of the constant current circuit 11. As a result, the transistor Q ₁₁ that operates as a buffer amplifier is supplied with a constant bias current from the constant current circuit 11 at its base and outputs a constant voltage. Further, the transistor Q ₁₇ turns off when the constant current circuit 11 starts operating.

[0037] Here, for example, if the emitter area of the transistor Q ₁₅ is three times the emitter area of the transistor Q _16, the voltage between the emitter and base of the transistor Q ₁₆ V
_BE16 can be expressed in two ways as shown below.

V _BE16 = (kT / q) ln (I _C14 / I ₀ ) V _BE16 = (kT / q) ln (I _C13 / 3I ₀ ) + R ₁₂ ×
I _C13 However, where, k: Boltzmann's constant T: absolute temperature q: electron charge I _0: a reverse saturation current of the transistor.

Therefore, (kT / q) ln (I _C14 / I ₀ ) = (kT / q) ln
(I _C13 / 3I ₀ ) + R ₁₂ × I _C13. If I _C13 = I _C14 in this formula, I _C13 = (kT / q) ln3 / R ₁₂ .

As a result, if the collector current of the transistor Q ₁₂ is I _C12 , then I _C12 = I _C13 = (kT / q) ln3 / R _12, and the output constant voltage V _OUT is the diode D
Assuming that the forward voltage of ₁₁ · D ₁₂ is respectively V _D11 · V _D12 , V _OUT = V _D11 + V _D12 + R ₁₁ × I _C12 = V _D11 + V _D12 + (R ₁₁ / R ₁₂ ) × (kT / q) ln
3

By the way, in this constant voltage circuit, a parasitic capacitance C ₁₁ exists at both ends of the resistor R ₁₄ . Therefore, in the inspection of the integrated circuit portion in the manufacturing process of the constant voltage circuit, if a power supply having a steep rise is used, the transient current I _n11 is _generated through the parasitic capacitance C ₁₁ even when the resistor R ₁₄ is open. It will flow and supply current to the base of transistor Q ₁₇ . Then, the transistor Q ₁₇ becomes the transistor Q ₁₃
The collector voltage is further supplied to operate, and the constant voltage circuit operates in the same manner as above.

[0042] In contrast, in the present voltage regulator, since it has a test pad P _11, similar to the constant-voltage circuit of the first embodiment of the resistance at a current meter using the test pad P ₁₁ The current flowing through R ₁₄ can be measured. And
By obtaining the resistance value of the resistor R _{14 from} this current, it is possible to determine whether or not the resistor R ₁₄ is in the open state.

[Embodiment 3] The following description will discuss Embodiment 3 of the present invention with reference to FIG.

The constant voltage circuit according to this embodiment is formed of a monolithic integrated circuit, and as shown in FIG.
Transistor Q that constitutes an emitter follower circuit in the output stage
₂₁ and a current mirror circuit for giving a base current to the transistor Q ₂₁ .

The collector of the transistor Q ₂₁ is connected to the power supply to which the power supply voltage V _CC3 is applied, and the base is connected to the collector of the transistor Q ₂₃ forming the current mirror circuit. The current mirror circuit is a transistor Q
₂₂ · Q ₂₃ is constituted by the transistor Q ₂₂ is connected to a power source via an emitter resistor R _21, the transistor Q ₂₃ is an emitter connected to the power supply directly. Also,
The bases of the transistors Q ₂₂ and Q ₂₃ are both connected to the collector of the transistor Q ₂₂ .

The anode of the diode D ₂₁ is connected to the collector of the transistor Q ₂₃ . Diode D ₂₁
The anode of the diode D ₂₂ is connected to the cathode of
The anode of the diode D ₂₃ is connected to the cathode of the diode D ₂₂ . Then, the cathode of the diode D ₂₃ is connected to the anode of the diode D _24, the cathode of the diode D ₂₄ is grounded.

On the other hand, the collector of the transistor Q ₂₂ is
The collector of the transistor Q ₂₄ is connected. The emitter of the transistor Q ₂₄ is grounded via the resistor R ₂₂ . The base of the transistor Q ₂₄ is connected to the anode of the diode D ₂₅ and also to the power supply via the resistor R ₂₃ . And the diode D ₂₅
The anode of diode D ₂₆ is connected to the cathode of
The cathode of the diode D ₂₆ is grounded.

In this constant voltage circuit, the transistors Q ₂₂ and Q
_A current mirror circuit composed of ₂₃ and a resistor R ₂₁ serves as a constant current circuit 21 for amplifying a current with a predetermined amplification factor, and this constant current circuit 21 functions as a first constant current circuit. . Further, the transistor Q ₂₄ , the diodes D ₂₅ and D _26, and the resistors R ₂₂ and R ₂₃ constitute a second constant current circuit that biases the first constant current circuit.

In the constant voltage circuit thus constructed, the emitter current of the transistor Q _{21 is} , for example, 5 m.
The case of flowing A will be described. In this case, _assuming that the DC current amplification factor of the transistor Q ₂₁ is 100, the collector current I _C23 flowing through the transistor Q ₂₃ allows for a double margin for ensuring the constant voltage operation, (5 mA / 100) × 2 = 100 μA.

If the resistance value of the resistor R ₂₁ is 6 kΩ and the amplification factor of the constant current circuit 21 is 10, the transistor Q
_The current I _C22 flowing through ₂₂ is 10 μA. On the other hand, the base-emitter voltage of the transistor Q ₂₄ is the diode D _25.
The forward voltage of the resistor R ₂₂ causes the forward voltage of the diode D ₂₆ (about 0.
7 V), the resistance value of the resistor R ₂₂ is 0.7 V / 10 μA = 70 kΩ.

Further, the current I _R23 flowing through the resistor R ₂₃ is
If the DC current gain of transistor Q ₂₄ is 100,
In consideration of the double margin for surely performing the constant voltage operation, (10 μA / 100) × 2 = 0.2 μA.

Here, if the range of the power supply voltage V _CC3 of the constant voltage circuit is 5 V to 15 V, I _R23 is 0.2 μA when V _CC3 is 5 V, so the resistance value of the resistor R ₂₃ . Is (5V-1.4V) /0.2 μA = 18 MΩ.

Next, when the resistance value of the resistor R ₂₃ is 18 MΩ, I _R23 is (15 V-1.4 V) / 18 MΩ≈0.75 μA even when the power supply voltage V _CC3 is 15 V.

As described above, according to this constant voltage circuit, the fluctuation of the bias current can be significantly suppressed with respect to the fluctuation of the power supply voltage V _CC3 .

The configurations described in the present embodiment and the above-described first and second embodiments are mere examples, and it is needless to say that other various configurations for achieving the same purpose can be considered.

[0056]

As described above, the constant voltage circuit of the present invention has the following features.
Equipped with an emitter follower circuit and a constant current circuit that gives a base current to the emitter follower circuit and is positively fed back.This constant current circuit is a start-up where one part of the positive feedback loop and the power supply start the constant current circuit. It is connected via a resistor, and an inspection pad for inspecting whether or not the starting resistor is in an open state is provided at a connection point between the positive feedback loop and the starting resistor.

As a result, it becomes possible to inspect whether or not the starting resistance is in the open state with the inspection pad, and the open state of the starting resistance can be easily found. Therefore, even if there is a parasitic capacitance in the constant voltage circuit and the constant voltage circuit operates due to the transient current flowing through the parasitic capacitance, it is possible to reliably determine whether the starting resistor is open.

Therefore, if this constant voltage circuit is adopted,
It is possible to surely remove the product in which the start-up resistor has a defective opening in the inspection stage, and it is possible to improve the reliability of the constant voltage circuit as the product.

Another constant voltage circuit of the present invention is an emitter follower circuit, a first constant current circuit which supplies a base current to the emitter follower circuit and has an amplifying function, and a bias for biasing the first constant current circuit. This is a configuration including a second constant current circuit.

Thus, the output current of the second constant current circuit becomes I / A, where A and I are the amplification factor and the output current of the first constant current circuit, respectively. In addition, the bias current of the second constant current circuit is I / (A ×), where h _FE is the direct current amplification factor of the output transistor of the second constant current circuit.
h _FE ). This current has a power supply dependency because it is supplied from the power supply, but the above amplification factor greatly suppresses fluctuations due to fluctuations in the power supply.

Therefore, if this constant voltage circuit is adopted,
The effect that the bias current is affected by the fluctuation of the power supply voltage can be reduced, and the reliability of the constant voltage circuit as a product can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a constant voltage circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a constant voltage circuit according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration of a constant voltage circuit according to a third embodiment of the present invention.

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

FIG. 5 is a circuit diagram showing the configuration of another conventional constant voltage circuit.

[Explanation of symbols]

1.1 constant current circuit 21 constant current circuit (first constant current circuit) 22 constant current circuit (second constant current circuit) Q ₁ · Q ₁₁ · Q ₂₁ transistor (emitter follower circuit) R ₂ · R ₁₄ resistance ( Starting resistance) P ₁ / P ₁₁ test pad (inspection pad)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 21/66 E 7630-4M 27/04 21/822

Claims (2)

[Claims] 1. A constant voltage circuit formed as a monolithic integrated circuit, comprising: an emitter follower circuit; and a constant current circuit which applies a base current to the emitter follower circuit and is positively fed back. One part of the feedback loop is connected to the power supply via a starting resistor that starts the constant current circuit, and it is checked whether the starting resistor is open at the connection point between the positive feedback loop and the starting resistor. A constant voltage circuit, which is provided with a test pad for inspection. 2. A constant voltage circuit formed as a monolithic integrated circuit, comprising: an emitter follower circuit; a first constant current circuit which supplies a base current to the emitter follower circuit and which has an amplifying function; and a first constant current circuit. A constant voltage circuit comprising: a second constant current circuit for biasing.