JP2910003B2 - Low voltage operation temperature stability characteristic current source circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IC (integrated circuit) used for consumer or industrial equipment requiring low voltage operation.
The present invention relates to a low-voltage operation temperature stability characteristic current source circuit for supplying an internal temperature stability characteristic constant current source.

[0002]

2. Description of the Related Art A constant current source which is stable with respect to temperature (a constant current source having temperature stable characteristics) requires a low voltage operation. The reason for this is to make the integration range of the integration circuit or the like constant so as not to cause circuit saturation. Such a constant current source is widely used, for example, for camera ICs, and has many other applications, and has a wide application range. FIG. 2 shows an example of a conventional circuit of a constant current source having a temperature stable characteristic. The circuit shown in FIG. 2 uses the current Is of the current source 10 to obtain a stable output current Iout with respect to temperature. Q14, Q15,
Q17 and Q18 are PNP transistors whose emitters are connected to a + power supply. Q11, Q
12, Q13 and Q16 are NPN transistors, the emitter of Q11 is directly connected to the emitter of Q12 and Q13 via a resistor R13, and the emitter of Q16 is connected to a resistor 12
Are grounded respectively. The output of current source 10 is connected to resistor R11 and the base of transistor Q12, which is connected to the collector and base of transistor Q11, whose emitter is directly grounded. The collector of transistor Q12 is connected to the collector and base of transistor Q14 and the base of transistor Q15. The collector of transistor Q13 is connected to the collector of transistor Q15 and the base of transistor Q16. The base of transistor Q13 and Q
The emitter of the transistor Q16 is connected to the collector of the transistor Q16.
A collector and a base of 17 and a base of Q18 are connected respectively.

The temperature characteristic Vbe of the base-emitter voltage of the transistor Q11 is approximately -2 mV / degree C (approximately-
3300 ppm / degree C), and the temperature characteristic of the voltage between both ends of the resistor R11 is +3300 ppm / degree C. Therefore,
These temperature characteristics cancel each other to produce a voltage Vref that is stable with respect to temperature. The output current Iout of the circuit of FIG.
It is represented by the following equation (1). Iout = Vref / R12 (1) In equation (1), the output current Iout is stable with respect to temperature.

[0004]

However, the above-mentioned conventional temperature stable characteristic current source circuit requires a minimum operating voltage of about 1.5 V.
There is a problem that operation becomes impossible when the voltage drops to V. FIG. 3 shows a circuit for supplying a constant current proportional to the absolute temperature (an absolute temperature proportional constant current source circuit) generally used in an IC circuit. In FIG.
Q27 is a PNP transistor whose base is connected in common, and each emitter is connected to a resistor R23 to R2.
5 is connected to the + power supply. In addition, Q21 to Q23
Is an NPN transistor. The collector and base of transistor Q21 are connected to the collector of transistor Q24, and the emitter is grounded via resistor R21.
The collector of transistor Q22 is connected to the collector of transistor Q25, and the emitter is grounded. The collector of transistor Q23 is connected to the base and collector of transistor Q26, and the emitter is grounded via resistor R22. This constant current circuit is characterized by a low voltage (about 1
(Approximately V), and the effect of fluctuations in the power supply voltage is not affected by the cancellation of the Early effect. However, such an absolute temperature proportional constant current source circuit is added to the current source 1 in the conventional temperature stable characteristic constant current source circuit.
Even if it is used as 0, the minimum operating voltage is still about 1.5 V, and the above problem is not solved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and can operate up to a power supply voltage of less than about 1 V using an absolute temperature proportional constant current source. An object of the present invention is to provide a low-voltage operating temperature stable characteristic current source circuit that is stable with respect to temperature, more specifically, stable against fluctuations in power supply voltage, and that can respond to a decrease in the operating voltage of an IC.

[0006]

According to the present invention, there is provided an NPN type first transistor having a collector connected to a current source having an absolute temperature proportional characteristic, and an NPN type sixth transistor having a base connected thereto. An NPN-type second transistor having a base and a collector connected to the base of the first transistor, a PNP-type third transistor having a collector connected thereto, and a base and a base connected to the third transistor. A fourth transistor of a PNP type having a collector connected thereto, a fifth transistor of a PNP type having a base connected thereto, and a first resistor connected between the collector of the second transistor and ground; The collectors of the fourth transistor and the sixth transistor are connected, the emitters of the first and second transistors are grounded, and the sixth transistor is connected. Is connected to the positive power supply via the third, fourth and fifth resistors, respectively, by having a configuration in which the star is grounded via a sixth resistor and the emitters of the third, fourth and fifth transistors are respectively connected via the third, fourth and fifth resistors. This is to solve the above-mentioned problem.

[0007]

According to the structure of the present invention, a constant current source circuit which operates at a power supply voltage of about 1 V or less and is stable with respect to temperature can be realized. It can respond to a decrease in the operating voltage of the IC.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention shown in FIG. 1 will be described below. In the embodiment shown in FIG. 1, an NPN-type first transistor Q1 whose collector is connected to a current source 10 having an absolute temperature proportional characteristic, an NPN-type sixth transistor Q6 whose base is connected, NPN-type second transistor Q2 having a base and a collector connected to the base of one transistor Q1 and PNP having a collector connected thereto
Type third transistor Q3, and a P transistor having a base and a collector connected to the base of the third transistor Q3.
A NP-type fifth transistor Q5 having a base connected to the NP-type fourth transistor Q4, and a resistor R1 connected between the collector of the second transistor Q2 and ground.
The collector of the fourth transistor Q4 and the collector of the sixth transistor Q6 are connected, the emitters of the first and second transistors Q1 and Q2 are grounded, and the sixth transistor Q6 is connected via a series resistor R6. Low voltage operating temperature stable characteristic current source having a configuration in which the emitters of the third, fourth and fifth transistors Q3, Q4 and Q5 are connected to a positive power supply via series resistors R3, R4 and R5, respectively. Circuit.

The current source 10 supplies a current Is proportional to absolute temperature. The current source 10 uses the one shown in FIG.
First, the current source 10 will be described. Current source 10 of FIG.
If the area ratio between the transistors Q21 and Q22 is made ten times, the voltage VR generated at both ends of the resistor R21 becomes the following equation (2)
It is represented by VR = (kT / q) ln (I / Is)-(kT / q) ln ((I / 10) / Is) = (kT / q) ln10 (2) Therefore, the current I flowing through the resistor R21 is obtained. Is as follows: I = VR / R21 = (kT / qR) ln 10 (3) The temperature characteristic of this current I is as follows: (dI / dT) = (k / qR) ln10 = (I / T) (4), and becomes about +3300 ppm / degree C at T = 300 degree K (absolute temperature Proportional).

When the value of the resistor R1 is selected such that the current I1 flowing through the transistor Q2 and the current I2 flowing through the resistor R1 are equal in the low voltage operating temperature stable characteristic current source circuit of FIG. 1, the current I2 becomes I2 = Vbe ( Q2) / R1 (5) Here, Vbe (Q2) is a base-emitter voltage of the transistor Q2. Therefore, the current I2 is a current proportional to the voltage Vbe (Q2) (about -3300 ppm / degree C). Since the output current Iout = I1 + I2,
As a result, the temperature characteristics of the currents I1 and I2 cancel each other, so that a stable output current Iout can be obtained with respect to temperature. Moreover,
In the configuration of FIG. 1, operation is possible at a voltage of about 1 V or less. Further, since the collector-emitter voltage Vce of the transistors Q1 and Q2 is about 1 Vbe (Q2), the Early effect is cancelled, and the output current Iout is stable against fluctuations in the power supply voltage.

[0011]

As described above, according to the present invention,
It operates at a power supply voltage of about 1 V or less, and can realize a constant current source circuit that is stable with respect to temperature. The excellent effect of obtaining is obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a current source circuit according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an absolute temperature proportional constant current source according to the embodiment.

FIG. 3 is an explanatory diagram of a conventional temperature stable constant current source circuit.

[Explanation of symbols]

 Reference Signs List 10 current sources Q1, Q2, Q6 NPN transistors Q3, Q4, Q5 PNP transistors R1 to R6 Resistance

Claims (1)

(57) [Claims] An NPN-type first transistor having a collector connected to a current source having an absolute temperature proportional characteristic, an NPN-type sixth transistor having a base connected thereto, and a base of the first transistor. An NPN-type second transistor having a base and a collector connected thereto, a PNP-type third transistor having a collector connected thereto, and a PNP-type transistor having a base and a collector connected to the base of the third transistor. A fifth transistor of a PNP type having a base connected to the fourth transistor, a first resistor connected between the collector of the second transistor and ground, and a collector of the fourth transistor and a sixth resistor. The collectors of the transistors are connected, the emitters of the first and second transistors are grounded, and the sixth transistor is connected via a sixth resistor. A low-voltage operating temperature stability characteristic characterized in that it is grounded and the emitters of the third, fourth and fifth transistors are connected to a positive power supply via third, fourth and fifth resistors, respectively. Current source circuit.