JPH02238509A - Reference voltage circuit - Google Patents

Abstract

PURPOSE:To obtain the reference voltage having no dependency on the power supply fluctuation and the temperature fluctuation based on a 2nd power supply by obtaining the same temperature coefficient between the 1st and 2nd resistors and using a reference voltage source having no dependence on the power supply fluctuation and the temperature fluctuation. CONSTITUTION:A voltage follower which inputs the reference voltage V1 consists of an operational amplifier 1, a transistor TR 2, a 1st resistor 3, and a reference voltage source 5. The collector of the TR 2 is connected to an output terminal 6 and also to a 2nd power terminal 8 via a 2nd resistor 7. The temperature coefficients of both resistors 3 and 7 are set equal to each other so that R2/R1 is kept constant when the resistance values of the 1st and 2nd resistors are referred to as R1 and R2. Then the source 5 is stable to the power supply fluctuation and the temperature fluctuation. Thus it is possible to obtain a reference output that is subject to a 2nd power supply and not dependent on the fluctuation of both the power supply and the temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reference voltage circuit, and more particularly to a reference voltage circuit that is stable against temperature fluctuations and power supply fluctuations.

"Prior Art" A bandgap reference circuit as shown in FIG. 2 has been known as a reference voltage circuit that is stable against temperature fluctuations and power supply fluctuations. The configuration of this circuit will be explained below based on FIG.

Three transistors 13, 14, 15 are connected between the output terminal 11 and a first power terminal (low level) 12, and these transistors 13 to 15 are connected to a second power terminal (high level). 16 and the output terminal 11 from a current source 17 . is being supplied. The collector of the first transistor 13 is connected to the output terminal 11 via the first resistor 18, the collector of the second transistor 14 is connected to the output terminal 11 via the second resistor 19, and the collector of the second transistor 14 is connected to the output terminal 11 via the second resistor 19. The collector of the transistor 15 is directly connected to the output terminal 11. The base of the first transistor 13 is connected to the collector of the same transistor 13, and is also connected to the base of the next stage transistor 14.

The collector of transistor 14 is further connected to the base of transistor 15 in the next stage. The emitter of the second transistor 14 is connected to the third resistor 20? connected to the first power supply terminal 12 through the first and third transistors 13
．． 15 emitters are directly connected to the first power supply terminal 12.

In the above configuration, the first, second, and third resistors 18,
19.Respectively the resistance value of 20 is R11R21R3, resistor 1
8.19 The current flowing through Il+IN, first, second,
Assuming that the base Φ emitter voltages of the third transistors l3, 14.15 are VB■1, VB■2, and VBE3, respectively, the current Ir flowing through the resistor 20 (R3)? 3 is as below (1
) is given by the formula.

I n3= (VBIEI Vna2) / R3
- (1) On the other hand, the base-emitter voltage VB of a transistor is generally expressed by the following equation (2).

VBH=VT anon (Ic/Is) −
(2) Here, V. The formula =kT/q (k: Boltzmann's constant, T: absolute temperature, q: electron charge) holds,
Ic is the collector current, and L is the saturation current. Therefore, (
Equation 1) can be expressed by Equation (3) below.

■+? 3= {VT +11n(I1 /I2)}/R
3... (3) Cocote, emitter grounding current amplification factor β of transistor 14
. is β. >>1, the voltage drop (2) of the resistor 19 (R2) is given by the following equation (4).

V2 Misaki R2●IR3 = (R2 /R3)-vT@non(L/I2)...
・(4) Set the output voltage to V. Then V. is expressed by the following formula (5).

Vo “Vna3+ (R2 / R3)”
VT●non (Is/Iz) ... (5) This V. When is differentiated with respect to temperature T, the following equation (6) is established.

δVo δT Here, in order to do so, the following equation (7) needs to hold true from equation (6).

゛1゛That is, R21R3+It+Work2 that satisfies this formula (7)
By selecting , temperature dependence can be eliminated.

In this bandgap reference circuit, as is clear from equation (5), the influence of temperature on saturation current I8 is eliminated, and R. ，
By selecting R3, L and I2, the temperature dependence of VBH is removed and extremely stable temperature characteristics can be obtained. Also, the current value I changes due to fluctuations in the power supply voltage. Even if changes, VB+! If the fluctuation in 3 is small and can be ignored, the output voltage ■.

is constant.

[Problems to be Solved by the Invention]However, in the conventional reference voltage circuit described above, the first
It is possible to obtain a reference voltage that does not depend on temperature fluctuations with the second power supply as a reference, but it is not possible to obtain a reference voltage that does not depend on temperature fluctuations with the second power supply as a reference. Also,
R2 r R3+ It so as to satisfy formula (7)
When +I2 is selected, the voltage between the first power supply terminal and the output terminal is determined to be approximately 1.2 rVJ, and there is a drawback that an arbitrary reference voltage cannot be obtained.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a reference voltage circuit that can obtain an arbitrary reference voltage that does not depend on temperature fluctuations and power fluctuations based on a second power supply.

[Means for Solving the Problems] A reference voltage circuit according to the present invention includes an operational amplifier, a reference voltage source connected between a positive phase input terminal of the operational amplifier and a first power supply terminal, and a reference voltage circuit connected to the operational amplifier. a first resistor connected between the negative phase input terminal of the amplifier and the first power supply terminal; and a base of the operational amplifier-6? a transistor connected to a positive phase output terminal, an emitter connected to a negative phase input terminal of the operational amplifier, and a collector connected to a reference voltage output terminal; and a transistor connected between the collector of this transistor and a second power supply terminal. It is characterized by comprising a second resistor.

[The voltage of the reference voltage source is V1, and the resistance value of the first resistor is R.
z Let the resistance value of the second resistor be R2.

The operational amplifier, the transistor, and the first resistor constitute a voltage follower, and the voltage V of the reference voltage source is equal to the voltage appearing across the first resistor. Therefore, the current flowing through the first resistor is Vl /Rl, and assuming that the base current of the transistor and the input current of the amplifier can be ignored, the collector current of the transistor is also Vl
■/R■, and the voltage across the second resistor is R2
(Vl/Rl). Therefore, by setting the temperature coefficients of the first resistor and the second resistor to be equal and using a reference voltage source that does not depend on power supply fluctuations and working temperature fluctuations, power fluctuations with respect to the second power supply as a reference. An independent output voltage is obtained. Furthermore, the output voltage can be set to any value by changing the ratio between RI and R2.

[Example] Next, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing the configuration of a reference voltage circuit according to an embodiment of the present invention. The operational amplifier circuit 1 has its positive phase output terminal connected to the base of the transistor 2 to drive the transistor 2. The emitter of the transistor 2 is fed back into the negative phase input terminal of the operational amplifier 1 and is also connected to the first power supply terminal 4 via the first resistor 3 . The positive phase input terminal of the operational amplifier 1 is connected to the first power supply terminal 4 via a reference voltage source 5 that generates a reference voltage v1. That is, the operational amplifier 1, the transistor 2, the first resistor 3, and the reference voltage source 5 constitute a voltage follower that receives the reference voltage (1) as an input. Further, the collector of transistor 1 is connected to an output terminal 6 and is also connected to a second power supply terminal 8 via a second resistor 7.

In the circuit of this embodiment configured as described above, the resistance values of the first resistor 3 and the second resistor 7 are now set to R, respectively.
, R2. The first, which is the output of the voltage follower
Since the voltage across the resistor 3 is equal to the base voltage V, the value of the current flowing through the resistor 3 is V. /R. Here, assuming that the base current of transistor 2 and the input current of operational amplifier 1 can be ignored, the collector current of transistor 2 is also vi /Rl, and the voltage across the second resistor 7 is (R2 /R,)V ．． becomes.

Therefore, in order to keep R2/Rl constant, the temperature coefficients of the first resistor 3 and the second resistor 7 are set to be equal, and the reference voltage source 5 is one that is stable against temperature fluctuations and power supply fluctuations. If selected, it is possible to obtain a reference output that is independent of temperature and power supply fluctuations and that is based on the second power supply. This reference output can be arbitrarily set by the ratio of R1 and R2 or the value of the reference voltage v1.

=9 [Effect of the invention] As explained above, according to the present invention, the reference output
Since it is determined by the ratio of the resistor to the second resistor and the peak power of the reference voltage source, the temperature coefficients of the first resistor and the second resistor are equal, and the power supply fluctuation φ temperature fluctuation By using a reference voltage source that does not depend on the second power supply, a reference voltage that is resistant to power supply fluctuations and temperature fluctuations with respect to the second power supply can be obtained. Furthermore, by setting the ratio between the resistance value of the first resistor and the resistance value of the second resistor, an arbitrary reference voltage can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a reference voltage circuit according to an embodiment of the present invention;
FIG. 2 is a circuit diagram of a conventional bandgap reference circuit. 1; operational amplifier, 2; transistor, 3; first resistor, 4; first power supply terminal, 5; reference voltage source, 6; output terminal, 7; second resistor, 8; second power terminal

Claims (1)

[Claims] (1) between an operational amplifier, a reference voltage source connected between the positive phase input terminal of the operational amplifier and the first power supply terminal, and the negative phase input terminal of the operational amplifier and the first power supply terminal; a transistor having a base connected to the positive phase output terminal of the operational amplifier, an emitter connected to the negative phase input terminal of the operational amplifier, and a collector connected to the reference voltage output terminal; A reference voltage circuit comprising a second resistor connected between the collector of the transistor and a second power supply terminal.