JPH11231955A - Reference current source circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reference current source circuit capable of reducing the temperature dependence of a reference current generated and outputted from the reference current source circuit or changing it as required, and also of suppressing the increase in a circuit scale. SOLUTION: A reference current source circuit 100 is constituted of a 1st reference current source circuit part 10 utilizing parasitic bipolar transistors, a 2nd reference current source circuit part 20 utilizing thermal voltage and a current addition circuit part 30 for mutually adding currents I11 , I21 respectively generated from the circuit parts 10, 20 at a prescribed ratio and outputting a current equivalent to the added current as a reference current IOUT.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference current source circuit used in a semiconductor integrated circuit, and more particularly, to a complementary current source circuit.
The present invention relates to a reference current source circuit applied to an integrated circuit device having an S transistor configuration.

[0002]

2. Description of the Related Art In recent years, as the integration density of an integrated circuit device constituted by complementary MOS transistors (hereinafter referred to as CMOS) has been improved, an analog circuit having a MOS transistor structure has been desired. By the way, in an analog circuit, a current source is generally used in many cases, so that a variation in a current value of each current source greatly affects circuit characteristics of the analog circuit. Many current sources used in analog circuits have a circuit configuration that generates and outputs a current proportional to a reference current by a current mirror configuration, so that the reference current source is not affected by the manufacturing process (process) or the surrounding temperature environment. Things are desired.

Conventionally used reference current source circuits include, for example, “Analog Integrated Circuit Design Technology for Ultra LSI (Lower Volume)”, 1990, p. R. Gray / R. G. FIG. As described in Meyer co-author, translated by Nagata Joi, Baifukan, etc., a circuit using a parasitic bipolar, a circuit using a thermal voltage, a circuit using a band gap voltage, and the like are known.

[0004] These reference current source circuits will be sequentially described with reference to FIGS. 3 to 5. Here, a circuit configuration using a pnp bipolar transistor (hereinafter referred to as a pnp bipolar transistor) formed by a CMOS process using a p-type substrate is shown. Current Source Circuit Using Base-Emitter Voltage V _BE of Parasitic Bipolar Transistor as Reference Voltage As shown in FIG. 3, a reference current source circuit IS1 has a pnp bipolar Q1 having a base and a collector grounded, and one end grounded. And a feedback circuit F1 connected to the pnp bipolar Q1 and the resistor R1 arranged in parallel.
And a p-type MOS transistor M5 that outputs a predetermined reference current I _OUT according to the output of the feedback circuit.

The pnp bipolar Q1 is a parasitic bipolar formed by a CMOS process forming the feedback circuit F1. The feedback circuit F1 is a p-type MOS transistor M
1 and an n-type MOS transistor M3 are connected in series to the power supply _Vdd and the emitter of the pnp bipolar Q1, while a CMOS configuration including the p-type MOS transistor M2 and the n-type MOS transistor M4 is connected to the power supply _Vdd and It is connected in series to the resistor R1.

That is, the two CMOS configurations have the power supply V _dd
Are connected in parallel to each other, and the intermediate contact of each CMOS configuration is
The gates of the n-type MOS transistors M3 and M4 and p
It is connected to the gates of the type MOS transistors M1 and M2. One end of the p-type MOS transistor M5 has a power supply V _dd.
And the gates are p-type MOS transistors M2 and n
It is connected to an intermediate contact of a CMOS configuration composed of a type MOS transistor M4.

In such a circuit configuration, the feedback circuit F
1, based on V _{BE1 of} pnp bipolar Q1,
The same potential is applied to the emitter of the pnp bipolar Q1 and the other end of the resistor R1, and the pnp bipolar Q1 and the resistor R
A current I ₁ equivalent to ₁ flows down. At this time, the p-type MOS
The value of the current I _OUT output from the transistor M5 and p
relationship between the resistance value r ₁ of the V _BE1 and the resistor R1 of np bipolar transistor Q1 is expressed as follows.

[0008] That is, the resistance R is set by the p-type MOS transistor M5.
A reference current I _OUT having a current value equivalent to the current I ₁ flowing down to ₁ is output.

Current source circuit using thermal voltage as reference voltage As shown in FIG. 4, a reference current source circuit IS2 is composed of pnp bipolar transistors Q1 and Q2 having a base and a collector grounded.
A resistor R2 having one end connected in series to the emitter of the pnp bipolar Q2, a pnp bipolar Q1 arranged in parallel, a feedback circuit F2 connected to the resistor R2 and the pnp bipolar Q2, and an output of the feedback circuit. P-type MOS transistor M that outputs a predetermined reference current I _OUT
5 is provided.

Here, pnp bipolar Q2 is pnp bipolar Q2.
It is formed so as to have n times the area of bipolar Q1. Note that the same components as those of the circuit shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted. In such a circuit configuration, the feedback circuit F2 sets the pnp bipolar Q1 based on the V _BE of the pnp bipolar Q1.
And the same potential is applied to the other end of the resistor R2 and the emitter of
pnp bipolar Q1, and the equivalent current I ₂ flows down to the resistor R2 and the pnp bipolar Q2.

At this time, the difference between V _{BE1 of the} pnp bipolar Q1 and V _{BE2 of} Q2 is applied to the resistor R2. If the thermal voltage is VT, the voltage is output from the p-type MOS transistor M5. relationship between the value of current I _OUT and the resistance value r ₂ of the resistor R2 that is expressed as follows. Here, V _T = kT / q, where k is Boltzmann's constant,
T is the absolute temperature and q is the electron charge.

Current Source Circuit Using Bandgap Voltage as Reference Voltage As shown in FIG. 5, a reference current source circuit IS3 has a base and a collector in addition to a circuit configuration equivalent to the reference current source circuit IS2 shown in FIG. Pnp bipolar Q3 grounded
A resistor R3 having one end connected to the emitter of the pnp bipolar Q3, the other end connected to the p-type MOS transistor M5, a resistor R4 having one end grounded, and a series connection to the other end of the resistor 4. n-type MOS transistor M6
And one input is a p-type MOS transistor M5 and a resistor R
3, an operational amplifier OP having an input connected to the connection point of the n-type MOS transistor M6 and the resistor R4, and an output connected to the gate of the n-type MOS transistor M6. ing.

Here, the pnp bipolars Q2 and Q3 are:
The resistor R3 is formed to have an area n times as large as the pnp bipolar Q1, and the resistor R3 is formed to have a resistance value x times the resistor R2. Note that the same components as those of the circuit shown in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

In such a circuit configuration, the p-type MOS
Current I _A flowing down the transistor M5, the (2)
The ratio x (that is, the proportionality factor x) of the resistance value of the resistor 3 to the resistance R2 and the area ratio of the pnp bipolar Q2 and Q3 to the pnp bipolar Q1 formed at the next stage through which this current flows. By appropriately selecting n (that is, the proportional coefficient n), the value of the current I _OUT output from the n-type MOS transistor M6 is expressed as follows.

[0015] Here, V _BE3 is a base-emitter voltage of the pnp bipolar Q3, and r ₄ is a resistance value of the resistor R4.

[0016]

Reference current source circuit IS1~IS3 described above [SUMMARY OF THE INVENTION] are both generates a reference current I _OUT of the object by applying a known voltage to a known resistor, and outputs. However, in the above-described reference current source circuit IS1 using the parasitic bipolar, the V _{BE of} the parasitic bipolar usually has a negative temperature coefficient, while the resistance formed by the diffusion layer or the polysilicon is positive. Because of the temperature dependency, the reference current I _OUT represented by the above equation (1) has a problem that it exhibits a large negative temperature dependency.

Further, in the reference current source circuit IS2 using thermal voltage shown above, since the thermal voltage V _T has a positive temperature dependence, the reference current I _OUT represented by the above formula (2) Is smaller than that of the reference current source circuit IS1 using a parasitic bipolar transistor. However, in general, the temperature dependency of the thermal voltage _{VT and} the temperature dependency of the resistance have different tendencies, so that the temperature dependency cannot be completely eliminated. In reality, the reference current I _OUT is
Under the influence of temperature dependency of the large thermal voltage V _T, there is a problem that a positive temperature dependency.

Further, in the reference current source circuit IS3 utilizing the band gap voltage described above, by appropriately setting the proportional coefficients x and n in the above equation (3), the reference current within the operating range is obtained. The temperature dependency of I _OUT can be eliminated. However, since the reference current source circuit includes the operational amplifier, a bias current source and a voltage source for operating the operational amplifier are inevitably required, and there is a problem that the circuit scale is increased.

Therefore, the present invention solves the above problems,
The temperature dependency of the reference current generated and output by the reference current source circuit can be reduced or a desired tendency can be obtained.
It is another object of the present invention to provide a reference current source circuit capable of suppressing an increase in circuit scale.

[0020]

In order to achieve the above object, according to the present invention, a first transistor having a base and a collector grounded, a first resistor having one terminal grounded, and a first transistor having a grounded one terminal are provided. Applying the same potential to the emitter of the first transistor and the other terminal of the first resistor, causing an equivalent current to flow through the first transistor and the resistor to generate a first output current A first feedback circuit having a first reference current source circuit section, a second transistor having a base and a collector grounded, a third transistor having a base and a collector grounded, and one terminal By applying the same potential to the second resistor connected to the emitter of the third transistor and the other terminal of the emitter of the second transistor and the other terminal of the second resistor, the second resistor A second reference current source circuit unit having a second feedback circuit for causing a current equivalent to flow through the transistor, the second resistor, and the third transistor to generate a second output current; And a current addition circuit unit for adding the first and second output currents at a predetermined ratio to generate a reference current having a predetermined temperature dependency.

According to a second aspect of the present invention, in the reference current source circuit according to the first aspect, the current adding circuit section comprises:
The predetermined ratio is set so that the temperature dependency of the first output current and the temperature dependency of the second output current cancel each other. According to a third aspect of the present invention, there is provided a first transistor having a base and a collector grounded, a first resistor having one terminal grounded, and a second transistor having a base and collector grounded. A second resistor whose terminal is connected to the emitter of the second transistor, and the same potential is applied to the emitter of the first transistor, the other terminal of the first resistor, and the other terminal of the second resistor. And a feedback circuit that generates a predetermined reference current by causing an equivalent current to flow through the first transistor, the first resistor, the second resistor, and the second transistor. It is characterized by doing.

[0022] The invention described in claim 4 is based on claim 1,
4. The reference current source circuit according to 2 or 3, wherein the first, second, and third transistors are pnp-type bipolar transistors. Further, the invention according to claim 5 is the reference current source circuit according to claim 1, 2 or 3, wherein the first, second and third transistors are npn-type bipolar transistors.

As described above, the first reference current source circuit section constituting the reference current source circuit utilizing the parasitic bipolar, and the second reference current source circuit section constituting the reference current source circuit utilizing the thermal voltage are provided. And the respective output currents are added at a predetermined ratio by the current adding circuit section, whereby the temperature dependency of each output current generated by the first and second reference current source circuit sections has a desired tendency. Therefore, a reference current with reduced temperature dependency can be generated.

Further, by sharing the feedback circuits of the first and second reference current source circuit sections, the temperature dependence of the reference current is set to a desired tendency, and the increase in circuit scale is greatly suppressed. A reference current source circuit can be provided.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a reference current source circuit according to the present invention will be described with reference to FIG. In FIG. 1, a reference current source circuit 100 uses a reference current source circuit section 10 using a parasitic bipolar constituting a first reference current source circuit section and a thermal voltage forming a second reference current source circuit section. Reference current source circuit section 20 and current addition circuit section 30
And is configured.

The reference current source circuit section 10 has a configuration substantially the same as the circuit configuration shown in FIG. 3 as the prior art, and includes a pnp bipolar Q11 whose base and collector are grounded, a resistor R11 whose one end is grounded, , Pnp bipolar Q1
A feedback circuit F11 that applies the same potential to the other end of the emitter 1 and the resistor R11 and causes the same current to flow therethrough
And

The feedback circuit F11 has the same configuration as the feedback circuit F1 shown in FIG.
The S1, a predetermined output current corresponding to the current I ₁₁ flowing down the pnp bipolar Q11 and resistor R11, is flowing down to the current adding circuit 30 to be described later. The reference current source circuit section 20 has substantially the same configuration as the circuit configuration shown in FIG. 4 as a conventional technique, and has pnp bipolar Q21 and Q22 whose base and collector are grounded, and pnp bipolar at one end.
Resistance R21 connected to the emitter of bipolar Q22
And the emitter and the resistor R21 of the pnp bipolar Q21.
The same potential is applied to the other end of the pnp bipolar Q21,
Further, a feedback circuit F21 for flowing the same current is provided in series connection of the resistor R21 and the pnp bipolar Q22.

The feedback circuit F21 has the same configuration as the feedback circuit F2 shown in FIG.
Due to S2, pnp bipolar Q21 and resistor R2
Predetermined output current corresponding to 1 and the current I ₂₁ flowing down to the series connection of the pnp bipolar Q22 is flowing down to the current adding circuit 30 to be described later. The current adding circuit unit 30 includes a power supply V
p is connected in parallel between _dd and the connection point N, and the output from the reference current source circuits 10 and 20 is applied to each gate.
-Type MOS transistors M31 and M32, an n-type MOS having one end and a gate connected to a connection point N and the other end grounded
A transistor M34 and a gate connected to a connection point N;
And an n-type MOS transistor M35 having one end grounded.

Here, the p-type MOS transistor M31,
The size (gate width / gate length) of M32 is set in advance so as to have a predetermined ratio. In such a current adding circuit section 30, the reference current source circuit sections 10 and 20
Current I ₁₁ which is generated by, I ₂₁ is summed based on the p-type MOS transistor size of M31 and M32 (gate width / gate length) ratio, this current equivalent to current n
It is output as a reference current I _OUT by the type MOS transistors M34 and M35.

That is, the current output from the reference current source circuit section 10 which is a reference current source circuit using a parasitic bipolar has a negative temperature dependency, and is a reference current source circuit which is a reference current source circuit using a thermal voltage. Although the current output from the current source circuit section 20 has a positive temperature dependency, these tendencies of the temperature dependencies are different. There is no control.

Therefore, in the present embodiment, the current adding circuit is designed so that the tendency of the temperature dependence of the currents output from the reference current source circuit sections 10 and 20 cancels each other or has an arbitrary tendency. By forming the p-type MOS transistors M31 and M32 of the unit 30 with a predetermined area ratio at the time of design, the temperature dependency of the reference current I _OUT generated by the n-type MOS transistor M35 is reduced or set to a predetermined tendency. can do.

More specifically, the pn of the reference current source circuit 10 is
Assuming that the temperature dependency of V _BE of p bipolar Q11 is K ₁ and the temperature dependency of resistor R11 is K ₂ , the temperature dependency K _A of current I ₁₁ is approximately expressed as follows. K _A ≒ K ₁ −K ₂ (4) On the other hand, assuming that the operating temperature of the reference current source circuit 100 is T, the temperature dependency of the heat voltage can be generally expressed as 1 / T. temperature dependence K _B of the current I ₂₁ which is generated by is expressed as follows.

The _{K B = (1 / T)} -K 2 ··· (5) In addition, the output current I ₃ of the current adding circuit 30, p-type MO
Assuming that the coefficients based on the size (gate width / gate length) ratio of the S transistors M31 and M32 are A ₁ and A ₂ , respectively, they are expressed as follows. I ₃ = A ₁ · I ₁ + A ₂ · I ₂ (6) Here, the current addition coefficient X is defined as X = A ₁ · I ₁ / I ₃ (7). The temperature dependency K ₃ of the output current I ₃ of the addition circuit unit 30 is expressed as follows.

K ₃ = X (K ₁ −K ₂ ) + (1−X) · ((1 / T) −K ₂ ) (8) Therefore, the current addition coefficient X is set to an appropriate value. Thereby, the temperature dependency K ₃ of the output current I ₃ can be set to an arbitrary value (trend). For example, the temperature dependence K ₃ of the output current I ₃ (suppressed) completely abolished the in order to realize a reference current source circuit, K ₃ = 0 as a current addition coefficient X
May be set as follows to design the circuit.

X = ((1 / T) −K ₂ ) / ((1 / T) −K ₁ ) (9) Next, a second embodiment of the reference current source circuit according to the present invention. This will be described with reference to FIG. In FIG. 2, a reference current source circuit 40 is a pn with a base and a collector grounded.
p bipolar Q41 and a resistor R41 having one end grounded
The same potential is applied to the pnp bipolar Q42 whose base and collector are grounded, the resistor R42 whose one end is connected to the emitter of the pnp bipolar Q42, the emitter of the pnp bipolar Q41, and the other end of each of the resistors R41 and R42. applied to, p-type MOS transistor and the feedback circuit F41 for these to flow down the same current, and outputs a predetermined reference current I _{OU T} according to the output of the feedback circuit F41 M45
And

The feedback circuit F11 includes p-type MOS transistors M41 and M42 and an n-type MOS transistor M4.
3 and M44, and has the same circuit configuration as the feedback circuits F11 and F21 described above. That is, the resistor R41
Corresponds to the resistor R11 of the reference current source circuit unit 10 using the parasitic bipolar shown in FIG. 1, and the resistor R42 and the pnp
The series connection of the bipolar Q42 is based on the reference current source circuit section 20.
The current that flows through the resistor is a resistor R21 and a pnp bipolar Q
22 and the feedback circuit F41 includes feedback circuits F11 and F2 of the reference current source circuit units 10 and 20, respectively.
1 corresponds to a shared configuration.

Therefore, the current I ₄₁ has a negative temperature dependency, and the current I ₄₂ has a positive temperature dependency. Also, pn
current I _Q, the resistance R41 which flows down to the p bipolar Q41
I ₄₁ , the resistor R ₄₂ and the pnp bipolar Q
42 corresponds to the sum of the currents I ₄₂ flowing through the series connection of ₄₂ .

Therefore, the current I ₄₁ showing the negative temperature dependency
And an output corresponding to the current obtained by adding (adding) the current I ₄₂ showing the positive temperature dependency is generated and output as the reference current I _OUT by the p-type MOS transistor M45.
At this time, the temperature dependence of the reference current I _OUT output by the p-type MOS transistor M45 is arbitrary depending on the ratio of the current I ₄₁ flowing through the resistor R41 to the current I ₄₂ flowing in series connection of the resistor R42 and the pnp bipolar Q42. Can be adjusted and set.

Accordingly, the shared feedback circuit F41
A resistor R41, a resistor R42 and a pnp bipolar Q
In a simple circuit configuration in which the serial connection of 42 is connected in parallel, by appropriately setting the values of the currents I ₄₁ and I ₄₂ flowing down each of the resistor R ₄₁ and the serial connection of the resistor R ₄₂ and the pnp bipolar Q ₄₂ , It is possible to arbitrarily set the temperature dependence of the reference current I _OUT while significantly suppressing an increase in circuit scale.

Note that, in the above-described embodiment, p
Formed by a CMOS process using a mold substrate
Although the reference current source circuit using the bipolar is shown, a similar circuit is formed by forming an npn-type bipolar transistor using an n-type substrate and inverting the polarity of a power supply used for the reference current source circuit. It goes without saying that it can be configured.

[0041]

According to the reference current source circuit of the present invention, a first reference current source circuit portion forming a reference current source circuit utilizing a parasitic bipolar and a reference current source circuit utilizing a thermal voltage are formed. Each output current generated by the first and second reference current source circuit sections is combined with the second reference current source circuit section, and each output current is added at a predetermined ratio by the current addition circuit section. Can have a desired tendency, so that a reference current with reduced temperature dependence can be generated.

Further, by sharing the feedback circuits of the first and second reference current source circuit sections, the temperature dependence of the reference current is set to a desired tendency, and the increase in the circuit scale is greatly suppressed. A reference current source circuit can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a reference current source circuit according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the reference current source circuit of the present invention.

FIG. 3 is a circuit diagram showing a reference current source circuit using a parasitic bipolar transistor.

FIG. 4 is a circuit configuration diagram showing a reference current source circuit using a thermal voltage.

FIG. 5 is a circuit configuration diagram showing a reference current source circuit using a band gap voltage.

[Explanation of symbols]

10, 20 Reference current source circuit section 30 Current addition circuit section 40, 100 Reference current source circuit F11, F21, F41 Feedback circuit Q11, Q21, Q22, Q41, Q42 pnp bipolar R11, R21, R41, R42 Resistance

Claims (5)

[Claims] A first transistor having a base and a collector grounded; a first resistor having one terminal grounded;
By applying the same potential to the emitter of the first transistor and the other terminal of the first resistor, the first
An equivalent current flows through the transistor and the resistor,
A first reference current source circuit section having a first feedback circuit for generating a first output current; a second transistor having a base and a collector grounded; and a third transistor having a base and a collector grounded. By applying the same potential to the transistor, a second resistor having one terminal connected to the emitter of the third transistor, and the same potential to the emitter of the second transistor and the other terminal of the second resistor, A second feedback circuit configured to cause an equivalent current to flow through the second transistor, the second resistor, and the third transistor, and to generate a second output current. And a current adding circuit unit that adds the first and second output currents at a predetermined ratio to generate a reference current having a predetermined temperature dependency. . 2. The current adding circuit section sets the predetermined ratio such that the temperature dependency of the first output current and the temperature dependency of the second output current cancel each other. 2. The reference current source circuit according to claim 1, wherein: 3. A first transistor having a base and a collector grounded, a first resistor having one terminal grounded,
A second transistor having a base and a collector grounded; a second resistor having one terminal connected to the emitter of the second transistor; and a second resistor having the other end of the emitter of the first transistor and the first resistor. Terminal and the second
By applying the same potential to the other terminal of the resistor, the first transistor, the first resistor, and the second
And a feedback circuit that generates a predetermined reference current by causing an equivalent current to flow through the resistor and the second transistor. 4. The reference current source circuit according to claim 1, wherein said first, second and third transistors are pnp type bipolar transistors. 5. The reference current source circuit according to claim 1, wherein said first, second and third transistors are npn-type bipolar transistors.