JPH0476715A - Reference voltage generating circuit - Google Patents

Abstract

PURPOSE:To obtain a reference voltage not influenced by the current amplification factors of transistors(TRs) by automatically canceling the variation of a base current flowing into the bases of the 1st and 2nd TRs which are connected in common. CONSTITUTION:The 3rd and 4th TRs T1', T2' which are the same elements as the 1st and 2nd TRs T1, T2 are driven as the substitutes of the collectors of the TRs T1, T2 and the base current of the TRs T1', T2' is the same as that of the Trs T1, T2. Thereby, the variation of the base current is automatically canceled. Thereby, the reference voltage VREF is not influenced by the variation of the current amplification factors of the TRs due to temperature or dispersion.

Description

[Detailed Description of the Invention] The present invention is applicable to bipolar IC power supplies, voltage regulators,
In AC/DC converters, comparators, etc.
The present invention relates to a reference voltage generation circuit that supplies a reference voltage.

Figure 4 shows a voltage regulator employing a conventional reference voltage generation circuit 1, in which the collector of the reference voltage generation circuit 1 is connected to the input voltage line 2 via a resistor Rcl. The first whose emitter is connected to the ground via the resistor R2.
It consists of a transistor TI and a second transistor T2 whose collector is also connected to the input voltage line 2 via a resistor Rc2 and whose emitter is connected via a resistor R1 to the emitter of the first transistor T1. The bases of the two transistors TI and T2 are connected to each other and to the connection midpoint (a) of the resistors R3 and R4. A reference voltage Vref is generated between this base and the ground point. The emitter area of the second transistor T2 is selected to be eight times larger than the emitter area of the first transistor T1.

The collector outputs of the first and second transistors TI and T2 are connected to the non-inverting input terminal (+) and the inverting input terminal (
−). The output of this operational amplifier 3 is given to the base of the transistor TO, and the output Vo as a regulator is taken out from its emitter. now,
The collector currents of the first and second transistors TI and T2 are respectively Ic+ and ■c2, and the emitter current flowing through each transistor is r E"'; I C+ + I C2... (1
), the base-emitter conduction voltage V[lEl, VBE2 of each transistor Tl, T2 is Vsa
+=kT/q-1nI E/Is+...(2
) VaE2=kT/ q-1nI E/ I s2=・
・(3) becomes. However, k is Boltzmann's constant, q is electric charge, I Sl and I82 are transistors TI, respectively.
This is the reverse saturation current of T2. The difference ΔV [I
From equations (2) and (3), E is ΔVsl:=kT/q
-1nll:/I SE kT/q ・InIp
/■, 2 kT/ q・In I s2/ I s+...'・(
4) Here, since the emitter area of the second transistor T2 is selected to be eight times that of the first transistor T1, I S2 = 8 I S+. Therefore, equation (4) becomes ΔVaε=kT/q·ln8 (5). Since kT/q is 25.9mV, (5)
The formula% is the formula%. Note that since kT/q has a positive temperature coefficient, ΔVBE similarly has a positive temperature coefficient.

On the other hand, the reference voltage VREF is as follows: VREF=V[lEI+ 2 I E ′ R2=
V [lEl + 2 R2/ R+ ' △vBE・
...(6). Here, the first term VBE+ of equation (6)
has a negative temperature coefficient, and the second term 2R2/R,・
ΔV8E has a positive temperature coefficient. Therefore, when designing, adjust the positive temperature coefficient with the ratio of R2/R+ to
Adjustment is made so that the temperature coefficient of the entire REF becomes zero.

At this point, the first and second transistors TI and T2 described above
The operation requires a base current IB, and this base current is the sum of the base current 81 of the first transistor T1 and the base current IQ2 of the second transistor T2. Moreover, these base currents I! ll, I+
12 is ■. 5, ■. If 2 is the collector current, then 1a+=r. +/h FE I 82 = I C2/ h FE and is involved in the current amplification factor hFE. however,
As is well known, this current amplification factor hFE has a very large temperature dependence. Therefore, the value θ varies greatly depending on the temperature. In particular, since the temperature changes significantly at low hpE, the reference voltage VREF also changes, resulting in a problem that the output V O (=Ra/Ra·V HEF) of the regulator is affected by the temperature characteristics.

The present invention has been devised in view of these points, and is devised so that the reference voltage is not affected by fluctuations due to temperature or variations in the current amplification factor hFE of the transistor.

In order to achieve the above object, the present invention includes a first transistor whose emitter is connected to a reference potential point via a first resistor;
a second transistor whose emitter is connected to the emitter of the first transistor via a #12 resistor, and a reference voltage is obtained from the commonly connected bases of the first and second transistors. , a third transistor identical to the first transistor is connected to the collector side of the first transistor, and a second transistor is connected to the collector side of the first transistor.
A fourth transistor, which is the same as the second transistor, is connected to the collector of the transistor, and the bases of the third and fourth transistors are connected in common, and the bases of the first and second transistors are connected to the third and fourth transistors. A base current supply means for supplying the same current to the bases of the two is connected.

In this case, the base current supply means is constituted by a current mirror circuit driven by the base sides of the third and fourth transistors, and the output side of the current mirror circuit is connected to the fi
It may be connected to the base of the l and fJ82 transistors.

According to this configuration, the transistors Tl' and T2', which are the same elements as the first transistor T1 and the second transistor T2, respectively, are the same as the first transistor T1 and the second transistor T2.
l, act as a replacement for the collector of T2, T1'',
Since the base current of T2 is the same as the base current of TI and T2, fluctuations in the base current are automatically canceled and are substantially unaffected by temperature fluctuations and variations in the current amplification factor hFE. do not have.

Next 1st index Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1 in which the present invention is implemented, parts that are the same as those in the conventional example shown in FIG. In this embodiment, third and fourth transistors TI' and T2', which are the same as the first and second transistors T1 and T2, are connected to the collector sides of the first and second transistors Tl and T2 as shown. That is, the emitter of the third transistor TI' is connected to the collector of the first transistor T1, and the collector of the third transistor TI' is connected to the input voltage line 2 via the resistor Rcl, while the emitter of the fourth transistor T2' is connected to the collector of the second transistor T2, and the collector of the fourth transistor T2' is connected to the input voltage line 2 via a resistor Rc2.

The emitter area of this fourth transistor T2'' is selected to be eight times as large as the emitter area of the first and third transistors Tl and T1'', similar to the emitter area of the second transistor T2. Fourth transistor Tl', T
2” bases are connected in common and the current mirror circuit 4
is connected to the input side of This current mirror circuit 4
is a pair of transistors T3. The transistor T4 consists of a transistor T4 and resistors R5 and R6, and its output side, that is, the collector of the transistor T4, is connected to the bases of the first and second transistors TI and T2.

In this circuit, a current flows through the first and second transistors TI and T2, and a current flows through the third and fourth transistors Tl' and T2.
The current IB+ flowing to the base of ゛ is Ie' = Ie, and since the current mirror circuit 4 provides more ゛ to the base side of the first and second transistors Tl and T2, the first
, the input impedance Zin to the second transistors Tl and T2 becomes (1), and a reference voltage VREF that is not affected by the current amplification factor hFE of the transistors is obtained.

Next, in the embodiment of FIG. 2, the third and fourth transistors T1'
, T2'' and the input voltage line 2, a current mirror circuit 5 is inserted in place of the resistors Rcl and Rc2.
This embodiment is the same as the embodiment shown in FIG. 1 except that the embodiment shown in FIG.

In addition, the embodiment shown in FIG. 3 is a current mirror circuit 6.7.8.
The third and fourth transistors T1'.

The currents It and I2 flowing to the collector side of T2' are routed separately, and the current difference between them is connected to the transistor T5. T6. It is fed back to the transistor T7 via the feedback circuit of the capacitor C1, and its emitter current is controlled. In this circuit, an input voltage is applied to a terminal 11, and an output voltage is taken out from a terminal 12. Note that the capacitor C1 functions as a phase adjustment capacitor to prevent oscillation.

As explained above, according to the present invention, the third and fourth transistors T1' and T2', which are the same elements as the first transistor TI and the second transistor T2, respectively, are the same as the first transistor TI and the second transistor T2. The base currents of the third and fourth transistors TI' and T2' are the same as those of the first and second transistors TI and T2, so the fluctuation of the base current is It is said that the reference voltage generated between the bases of the first and second transistors and, for example, a ground point is not affected by temperature fluctuations or variations in the current amplification factor hFE. effective.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a reference voltage generating circuit embodying the present invention, FIG. 2 is a circuit diagram of a second embodiment, and FIG. 3 is a circuit diagram of a third embodiment. FIG. 4 is a circuit diagram of a conventional example. T1...first transistor, T2...second transistor, Tl'...third transistor, T2°...fourth transistor. R1...second resistance, R2...first resistance, V
REF...Reference voltage, 2...Input voltage line, 4...Current mirror circuit.

Claims (2)

[Claims] (1) a first transistor having an emitter connected to a reference potential point via a first resistor; and a second transistor having an emitter connected to the emitter of the first transistor via a second resistor; In a reference voltage generation circuit that obtains a reference voltage from commonly connected bases of second transistors, a third transistor, which is the same as the first transistor, is connected to the collector side of the first transistor; A fourth transistor, which is the same as the second transistor, is connected to the collector, and the bases of the third and fourth transistors are connected in common, and the bases of the first and second transistors and the bases of the third and fourth transistors are connected in common. A reference voltage generation circuit characterized in that a base current supply means is connected to supply the same current to the reference voltage generation circuit. (2) The base current supply means is a current mirror circuit driven by the base sides of the third and fourth transistors, and the output side of the current mirror circuit is the first transistor.
, the reference voltage generating circuit according to claim 1, wherein the reference voltage generating circuit is connected to the base of the second transistor.