JPS61147317A - Reference voltage generating circuit - Google Patents

Abstract

PURPOSE:To decrease the temperature dependancy by using two transistors (TRs) whose collectors are connected to a common connecting point between a reference voltage generating terminal and a constant current source via a resistor. CONSTITUTION:An emitter of a TRQ7 acting like a constant current source is connected to a reference voltage terminal Vref, and collectors of the TRs Q3, Q4 are connected to the common connecting point via the resistors R1, R2 respectively. Bases of both the TRs are connected across a resistor R4, a base VB1 of the TRQ3 is connected to the reference voltage terminal Vref via a resistor R3 and a base VB2 of the TRQ4 is connected to common via a resistor R5 and a TRQ5. Since both the base voltages VB1, VB2 depend on a reciprocal of the voltage gain of the TRs Q3, Q4, even when collector voltages VC1, VC2 are fluctuated, the effect is very less.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor integrated circuit, and particularly to a reference voltage generation circuit used as a constant voltage source in an analog tC circuit.

[Conventional technology]

As is already known, reference voltage generation circuits are broadly divided into methods using an avalanche breakdown diode and methods using a band gear/X preference using an energy band within a semiconductor.

The purpose of both methods is to improve the temperature dependence of the generated reference voltage, but here a reference voltage generating circuit using the latter method will be outlined with reference to FIG. The circuit shown in FIG. 3 is basically a reference voltage generating circuit that utilizes the energy band between the base and emitter of a transistor, and the generated reference voltage Vref can be expressed by the following relational expression. That is, Vref = (R3+Ra +Rs)
' (Va+Vsz)“ /Ra+Vmt.

−−−−−−・・−１−−−−−−−・・ (1
1 = (R, I + Ra +, -, Rs)' VT
' ln (N)/Ra+Vmt. , −・−−1−−
・-・---(2) Here, V□, ■, 2 are the base potentials of transistors Q31Q4, vllEo is the base-emitter potential of transistor Q, and VT is kT/
In the constant denoted by q, k is the Boltzmann constant, T is the absolute temperature, q is the electric charge, and in' (N) is the transistor Q3.
.

It is the natural logarithm of the emitter ratio N of Q4.

The VIE of transistor Qs has a negative temperature coefficient due to the base-emitter junction, while each resistor R3+Ra, Rs
has a positive temperature coefficient, and v7 also has temperature dependence. Therefore, the reference voltage Vref is calculated using the above formula +11, (
2) Temperature compensation is performed by appropriately selecting each resistor and the emitter ratio of transistors Q3 and Q4. In this case, transistors Q, ,Q, and resistors R+, R
A constant current circuit is formed by z, and R,=RZ, and the current 11.1□ flowing therein has a current mirror configuration, so when matching is achieved, I,=lz.

Further, the emitter ratio is the emitter area ratio of a transistor, but it can be equivalently replaced with the ratio of the number of transistors arranged in parallel.

[Problem that the invention seeks to solve]

In the above configuration, the constant current sources formed by transistors Q+ and Qz supply equal current to transistors Q3 and Qa. However, if the consistency of the constant current sources deviates due to some factor, In the case of I, a change in the current value supplied to Q3 and Q4 appears as a change in the base potential V□+VlK, and the reference voltage Vr
This causes fluctuations in ef.

In this case, the factors that cause mismatch exist in the elements themselves that make up the circuit, and when integrated into an IC, there are large variations in characteristics compared to PNP (NPN) transistors, and variations in characteristics due to wiring length in pattern design. , variations in the manufacturing process, etc. are considered, which cause mismatch in the constant current circuit and cause fluctuations in the reference voltage Vref.

[Means and effects for solving the problems] The present invention provides a reference voltage generation circuit that solves the above problems, and the means is to connect the collector to the reference voltage generation terminal via a first resistor. and a constant current source, a first transistor having a base connected to the reference voltage generation terminal via a third resistor, and a collector connected to the common contact via a second resistor. a second resistor whose base is connected to the reference voltage generation terminal via the third resistor and the fourth resistor;
a third transistor whose collector is connected to a common contact between the base of the second transistor and the fourth resistor via a fifth resistor and whose emitter is grounded; The base potential of the transistor and the base potential of the second transistor are set by reciprocals of the voltage gains of the first transistor and the second transistor.

〔Example〕

FIG. 1 is a circuit diagram of an embodiment of a reference voltage generating circuit according to the present invention. As is clear from FIG. 1, the transistor QllQz, transistor Q8, and transistor Q, which constitute the conventional constant current source, are removed, and the collector of the transistor Q as the first transistor, the resistor R, and the The base of transistor Q6 and the collector of transistor Q4 as the second transistor and resistor R2
and the base of transistor Q1° are connected. Further, the resistor R+=Rz, the reference voltage Vref is generated from the reference voltage generation terminal Vref (same reference symbol for convenience), and the transistor Qs as the third transistor and the third . 4th. Fifth resistor R13゜Ra,,Rs
is the same as before.

In such a configuration, transistor Q3.

The collector potential of Q4 is set to VC1+VC2, respectively, and the first
and the currents flowing through the second resistors R+ and Rt, respectively.
Ig, each voltage gain A@1. A (14 can be expressed as follows. That is, A@3=△V c + /△V m + = R+ /
T el -----(3) A, 4=△V cz/△
V tz = Rz / r e2 --- (4) Here, Tel and re2 are the transistor Q3,
Qs emitter resistance, rel=V? /I I
.

re2=Vy/Ig.

As is clear from equations (3) and (4), the base potentials V Ill * v@2 of transistors Q3 and Qa are h VCI .

1/A of VB is 93.1/A (14). Therefore, even if the current I,≠■2 occurs due to some factor as mentioned above, the error given to VIII,
It can be seen that the influence is extremely small, which is AO3) times and (1/A114) times. The reference voltage V ref is calculated using the formula (11
As shown in , ■□ greatly depends on the value of v0, but by using such a circuit configuration, the influence of VII + vmz on the fluctuation of r, ,■ can be made extremely small, As a result, the reference voltage Vref can be stabilized. In the conventional circuit shown in FIG. 3, transistor Q3. Since Q4 has no amplification effect, the fluctuation of I+, It is directly caused by V, 1°■,! This appears, causing fluctuations in the reference voltage Vref.

In the present invention, if the transistors Q3 and Qa have larger gains or the values of the resistors R+ and Rt are used, fluctuations in V□, V, and t can be suppressed to a smaller value. Note that the transistors Q, , J are constant current sources that make the power supply Vcc a constant current.

FIG. 2 is a circuit diagram of another embodiment of the reference voltage generating circuit according to the present invention. This circuit does not have a power supply terminal Vcc due to its circuit configuration, and receives current from the power supply through an external resistor R. In this case, the transistor Qs,
Ql and transistor Q1°.

Qll constitutes a constant current circuit, and transistor Q3
, Qa, etc. are the same as in the first embodiment.

As is clear from the figure, in the circuit of Figure 1, Vref.

Although three terminals for Vcc and GND were required, this circuit has two terminals for Vref and GND, which can simplify the circuit.

〔Effect of the invention〕

According to the present invention, even if a mismatch occurs due to some factor, temperature compensation can be reliably performed, and a reference voltage generation circuit with less temperature dependence can be provided.

[Brief Description of the Drawings] FIG. 1 is a circuit diagram of one embodiment of the reference voltage generation circuit according to the present invention, FIG. 2 is a circuit diagram of another embodiment of the reference voltage generation circuit according to the present invention, and FIG. 3 is a circuit diagram of another embodiment of the reference voltage generation circuit according to the present invention. is a conventional reference voltage generation circuit. (Explanation of symbols) Q, ~Q,...Transistor, R, -R,...Resistor, Vref...Reference voltage generation terminal, Vcc
......Power voltage terminal.

Claims (1)

[Claims] 1. A first transistor whose collector is connected to a common contact between a reference voltage generation terminal and a constant current source via a first resistor and whose base is connected to the reference voltage generation terminal via a third resistor; a second transistor whose collector is connected to the common contact via a second resistor and whose base is connected to the reference voltage generation terminal via the third and fourth resistors; a third transistor whose collector is connected to a common contact point between the base of the transistor and the fourth resistor via a fifth resistor and whose emitter is grounded, the base potential of the first transistor and the second transistor 1. A reference voltage generation circuit characterized in that a base potential of a transistor is set by a reciprocal of voltage gains of the first transistor and the second transistor.