JPH0546096Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a current generation circuit for generating temperature-dependent current, and particularly provides a current generation circuit that can be used at a low power supply voltage. This is what I am trying to do. (b) Prior Art A current generating circuit capable of generating a temperature-dependent current was previously filed by the same applicant as the present invention in Utility Application No. 109171/1983. As shown in FIG. 2, the current generating circuit according to the above application includes a current source transistor 1, a diode-connected first transistor 2 and a first resistor 3 connected in series.
a first current path 4 consisting of a diode-connected second transistor 5, a second resistor 6, and a third resistor 7 connected in series; voltage and the third resistor 7
The voltage comparison circuit 9 is configured to supply current from the current source transistor 1 to the first and second current paths 4 and 8 , and to compare the voltage obtained at one end with the voltage obtained at one end . The current flowing through the current source transistor 1 is controlled by the output signal of the current source transistor 1. Therefore, if the circuit configuration is as shown in FIG. 2, it is possible to provide a current generating circuit that can generate a current that changes according to changes in ambient temperature. (c) Problems to be solved by the invention However, the current generating circuit shown in FIG.
When used at a low power supply voltage (for example, 1.5V), it has the disadvantage of worsening dependence on the power supply voltage and the disadvantage of being susceptible to variations in each circuit element. In the current generating circuit shown in Fig. 2, the terminal voltage of the first resistor 3 is the maximum V _CC −V _BE (where V _CC is the power supply voltage and V _BE is the first transistor 2
The base-to-emitter voltage of current source transistor 1 is the emitter-to-collector voltage ( _VCE is omitted) of
Since the emitter-to-emitter voltage is less than V _BE , the differentially connected transistors 10 and 11 forming the voltage comparator 9 cannot be directly connected. For that reason,
In the current generating circuit shown in FIG. 2, PNP type transistors 12 and 13 are arranged between one end of the first and third resistors 3 and 7 and the differentially connected transistors 10 and 11, and the voltage is Adjustment is being made, but when the PNP type transistors 12 and 13 are arranged, the transistors 12 and 1
There is a risk that the offset voltage of 3 and variations in the load resistances 14 and 15 will adversely affect the circuit operation. (d) Means for solving the problem The present invention has been made in view of the above-mentioned points.One end of the first and second resistors are connected to the collector of the current reduction transistor, and the ends of the first resistor are connected in series with the first resistor. A first semiconductor element is connected to the second resistor, a third resistor and a second semiconductor element are connected in series with the second resistor, and the first and second
One end of the semiconductor element is commonly grounded through a resistor,
The voltage obtained at the connection point between the first resistor and the first semiconductor element and the voltage obtained at the connection point between the first and second resistors are respectively applied to first and second transistors constituting a differential amplifier circuit. the output signal of the differential amplifier circuit is supplied to the base of the current reduction transistor, and the output current is obtained from an output transistor whose base and emitter are commonly connected to the base and emitter of the current reduction transistor. It is characterized by the fact that (E) Effect According to the present invention, the voltage obtained at the connection point between the first resistor and the first semiconductor element and the voltage obtained at the connection point between the first and second resistors are directly connected to the voltage at the connection point between the first and second resistors. 1
and the base of the second transistor. (F) Embodiment Figure 1 is a circuit diagram showing an embodiment of the present invention.
16 is a current source transistor whose emitter is connected to the power supply +V _CC ; 17 is a first resistor whose one end is connected to the collector of the current reducing transistor 16; 18;
19 is a diode-connected first transistor connected in series to the first resistor 17, and 19 is a second transistor whose one end is connected to the collector of the current source transistor 16.
20 is a third resistor whose one end is connected to the other end of the second resistor 19; 21 is a diode-connected second transistor connected in series to the third resistor 20; 22 is the first and second resistor; A resistor for commonly grounding the emitters of transistors 18 and 21, 2
3, third and fourth transistors 24 and 25 whose emitters are commonly connected; a current mirror circuit 26 disposed between the collectors of the third and fourth transistors 24 and 25; and the third and fourth transistors 24. and a resistor 27 connected to the common emitters of 25 and 25, and 28 has an emitter connected to a power source, and a base connected to the third transistor 24 together with the base of the current source transistor 16.
is an output transistor connected to the collector of In the case of the current generating circuit shown in FIG. 2, the current I ₁ flowing through the first current path 4 is I ₁ = R ₃ /R ₁ R ₂ KT/qlnR ₃ /R ₁ ...(1) However, R ₁ , R ₂ , _R3 are the resistance values of the first, second, and third resistors 3, 6, and 7, K is the Boltzmann constant, q is the electron charge, T is the absolute temperature, and the current _I2 flowing in the second current path 8 is , I ₂ = 1/R ₂ KT/qlnR ₃ /R ₁ ...(2). The collector current T ₃ of the current source transistor 1 is I ₃ =KT/qR ₂ (R ₃ /R ₁ +1)lnR ₃ /R ₁ (3), and the current I ₃ has a temperature-dependent composition. Become something. Since the current generating circuit shown in FIG. 1 has the same circuit configuration as that shown in FIG. ), and the second resistor ₁₉ , the third resistor 29 and the second
The current flowing in the second current path consisting of the series circuit with the transistor 21 is the current I ₂ expressed by the above equation (2).
is equal to Therefore, current source transistor 16
The collector current of is equal to the current I ₃ shown in the above equation (3), and the current flowing through the output transistor 28 is also I ₃ . Therefore, the current generating circuit shown in FIG. 1 can also generate a current that is temperature dependent. In addition, the collector voltage of the current source transistor 16
V _C is: V _C = R ₄ I ₁ + V _BE1 + R ₇ I ₃ = (R ₅ + R ₆ ) I ₂ + V _BE2 +
R ₇ I ₃ ...(4) However, T ₄ , R ₅ , and R ₆ are the resistance values of the first, second, and third resistors 17, 19, and 20, R ₇ is the resistance value of the resistor 22, and V _BE1 is The base-emitter voltage _VBE2 of the first transistor 18 becomes the base-emitter voltage of the second transistor 21, and the load connected to the collector of the output transistor 28 is selected, and the output transistor 2
If the collector voltage of the output transistor 28 is set equal to the voltage V _C , the collector current of the output transistor 28 becomes independent of fluctuations in the power supply voltage. Furthermore, the circuit of FIG. 1 connects the bases of the third and fourth transistors 24 and 25 that constitute the differential amplifier circuit 23 directly to the
and the other ends of the second resistors 17 and 19. First resistor 17 and first transistor 18
The voltage at the connection point between the second and third resistors 19 and 20 is set to approximately V _BE1 +R ₇ I ₃ by the first transistor 18, and the voltage at the connection point between the second and third resistors 19 and 20 is approximately R ₆ I ₂ +V _BE2
+R ₇ I ₃ is set. Therefore, the voltages at both of the connection points become equal to or higher than V _BE , and the bases of the third and fourth transistors 24 and 25 of the differential amplifier circuit 23 can be directly connected to the connection point. Therefore, with the circuit configuration shown in FIG. 1, the number of elements can be reduced and a current generating circuit that is resistant to variations can be obtained. (g) Effects of the invention As described above, according to the invention, it is possible to provide a current generation circuit that can generate a current that has temperature dependence. Further, according to the present invention, it is possible to provide a current generation circuit that can generate a stable output current even if the power supply voltage fluctuates. Furthermore, according to the present invention, it is possible to provide a current generating circuit that operates at a low power supply voltage, has a small number of elements, and is resistant to variations.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional current generating circuit. Explanation of main figure numbers, 16... Current source transistor, 17, 19, 20... First, second, third resistor, 18, 21... First, second transistor, 2
3...Differential amplifier circuit, 24, 25...3rd, 4th
Transistor, 28... Output transistor.

Claims (1)

[Scope of utility model registration request] a current source transistor whose emitter is connected to a power source; first and second resistors whose one ends are commonly connected to the collector of the current source transistor;
a first semiconductor element having a PN junction connected in series to a resistor; a second semiconductor element having a PN junction connected in series to the second resistor via a third resistor;
a fourth resistor that commonly grounds one ends of the first and second semiconductor elements; a first transistor to which a voltage generated at a connection point between the first resistor and the first semiconductor element is applied to its base; a differential amplifier circuit comprising a second transistor differentially connected to which a voltage generated at the connection point between the second resistor and the third resistor is applied to the base; and an output signal of the differential amplifier circuit is connected to the current source transistor. and an output transistor whose emitter and base are commonly connected to the current source transistor and which generates an output signal at its collector.