RU2518974C2 - Source of reference voltage - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: device contains five transistors, two resistors and current source coupled between the power supply bus and output terminal, bases of the first and second transistors are connected to collectors of the first and fifth transistors, the first resistor is coupled between the common bus and emitter of the second transistor, the second transistor is coupled between the output terminal and connected emitters of the fourth and fifth transistors, emitters of the first and third transistors are coupled to the common bus, bases of the third, fourth and fifth transistors are joined with collectors of the first and fourth transistors, a collector of the third transistor is connected to the output terminal.

EFFECT: obtainment of thermally stable output voltage at values closed to double energy gap width.

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Description

 The device relates to the field of electrical engineering and can be used as a temperature-stable source of reference voltage (ION).

Known temperature-stable sources of reference voltage, determined by the doubled band gap of the semiconductor, the disadvantages of which include excessive complexity caused by the use of a large number of elements [U.S. Patent 4380706. Voltage reference circuit / Robert S. Wrathall.- Dec. 24, 1980], and the need for additional connection to a power supply source, and not just to a current source [Soklof S. Analog integrated circuits: Trans. from English - M .: Mir, 1988. - P.240, Fig. 33.27], which significantly complicates their use as a reference diode.

The closest technical solution adopted for the prototype is a Vidlar diode, shown in figure 1 [Soklof S. Analog integrated circuits: TRANS. from English.- M.: Mir, 1988.- P.206, Fig.3.33]. The disadvantage, or rather a feature of the prototype is the possibility of its use as a temperature-stable ion only when the reference voltage is close to the value of the band gap.

The problem to which the invention is directed, is to provide the claimed technical result - obtaining a temperature-stable output voltage at values close to double the band gap.

To achieve the claimed technical result, a prototype circuit containing the first and second transistors, the bases of which are connected to the collector of the first transistor, the third transistor, the base of which is connected to the collector of the second transistor, the first resistor connected between the common bus and the emitter of the second transistor, the second resistor connected the first output to the output terminal, a current source connected between the power bus and the output terminal, while the emitters of the first and third transistors are connected to a common bus, and the the vector of the third transistor is connected to the output terminal, the fourth and fifth transistors are introduced, the bases of which are connected to the collectors of the fourth and second transistors, the collector of the fifth transistor is connected to the collector of the first transistor, the emitters of the fourth and fifth transistors are connected to the second output of the second resistor.

The prototype diagram is shown in figure 1. A diagram of the inventive device is presented in figure 2. Figure 3 shows the simulation results.

The inventive ION (figure 2) contains five transistors (first to fifth), respectively, indicated by the numbers 1-5, two resistors, indicated by the numbers 6 and 7, and a current source 8 connected between the power bus and the output terminal, while the bases of transistors 1 and 2 are connected to the collectors of transistors 1 and 5, the resistor 7 is connected between the common bus and the emitter of transistor 2, the emitters of transistors 1 and 3 are connected to the common bus, the bases of transistors 3, 4 and 5 are connected to the collectors of transistors 2 and 4, the collector transistor 3 is connected to the output terminal, the resistor is 6 v connected between the output terminal and the combined emitters of transistors 4 and 5.

Before you consider the operation of the claimed device, consider the operation of the prototype circuit (figure 1), as it is necessary for comparative analysis. In this case, let us assume that the base currents of the transistors are negligible, and the load current is absent. The output voltage U _{o of the} prototype is determined by the value of the base-emitter voltage U _{be3 of} transistor VT3 and the voltage drop U ₂ on resistor R2, which can be described by the following expression:

where φ _t - = kT / q is the temperature potential; k is the Boltzmann constant; T is the absolute temperature; q is the electron charge; I ₂ and I ₃ are the emitter currents of transistors VT2 and VT3, respectively; I _s is the saturation current of the reverse biased pn junction proportional to its area; R ₂ is the resistance of the resistor R2.

To find the current I ₂ should take into account the voltage of the base-emitter U _be1 and U _be2, respectively, of the transistors VT1 and VT2 and the voltage drop U ₃ on the resistor R3, writing the expression:

or

where R ₃ is the resistance of the resistor R3; I ₁ is the emitter current of the transistor VT1; N is the ratio of the areas of the emitters of transistors VT2 and VT1.

The approximate relation (2) is valid when the currents I ₁ and I _{2 are} equal. From here you can determine the current

Differentiating expression (3), we can determine the dependence of the current increment I ₂ on temperature T:

Differentiating expression (1), we obtain

To find the increment dU _be3 , the dependence

where C is a constant coefficient determined by the production technology of the integrated transistor; E is the energy band gap at absolute zero, obtained by linear extrapolation from room temperature to absolute zero, equal to 1.205 V.

It can be shown that expression (5), taking into account (1), (4), (6), can be reduced to

Equating (7) to zero, at a constant current I ₃ , we obtain

Therefore, when the output voltage is determined mainly by the band gap, the instability of the output voltage is close to zero in temperature.

Since the sum of the currents I ₁ , I ₂ and I _{3 is} constant, the increment dI ₃ = -dI ₁ -dI ₂ , and with equal currents I ₁ , I ₂ , I ₃ and the approximate equality of the increments dI ₁ and dI ₂ taking into account ( 4) we get

Expression (7) taking into account (9) can be written in the following form:

The operation of the claimed device is similar to the work of the Vidlar diode (figure 1). However, the equality of the emitter currents I ₁ and I _{2 of the} transistors 1 and 2, respectively (Fig. 2) is provided more accurately by the current follower on the transistors 4, 5. Moreover, the current I ₂ is equal to the current I ₁ (as well as the emitter currents of the transistors 4 and 5) and is determined by the expression:

where R ₇ is the resistance of the resistor 7; N is the ratio of the emitter areas of transistors 2 and 1.

And the output voltage is also determined by the value of the base-emitter voltage U _{be4 of} transistor 4, which is described by the following expression:

where R ₆ is the resistance of the resistor 6; I ₃ is the emitter current of transistor 3. By differentiating expression (11), we can derive the equalities:

Differentiating expression (12), taking into account (6) and (11) we obtain:

Or, taking into account (9) and (13):

Therefore, the instability of the output voltage of the claimed device in temperature is close to zero at the output voltage, determined mainly by the doubled band gap.

Assuming that for the prototype circuit U _out = 2φ _t + E, and for the circuit of the claimed device U _out = 2 (2φ _t + E), we can obtain an estimate of the absolute change in the output voltage through a temperature increment. It is noteworthy that this estimate turns out to be the same for both schemes:

And since the output voltage of the claimed device is twice that of the prototype, the relative instability is half that.

Presented in figure 3, the simulation results reflect the dependence of the output voltage of the prototype (out2) and the claimed device (out1) on temperature. Moreover, for convenience of comparison, the voltage out2 is increased by 1.131 V. The deviation from the calculated value does not exceed 10%.

Thus, both the analysis and the data of circuit simulation confirm that the claimed technical result is achieved for the claimed device — a temperature-stable output voltage is obtained at values close to double the band gap.

Claims (1)

A voltage reference source comprising first and second transistors, the bases of which are connected to the collector of the first transistor, a third transistor, the base of which is connected to the collector of the second transistor, a first resistor connected between the common bus and the emitter of the second transistor, a second resistor connected to the output terminal by the first output , a current source connected between the power bus and the output terminal, while the emitters of the first and third transistors are connected to a common bus, and the collector of the third transistor is connected to output terminal, characterized in that the fourth and fifth transistors are introduced, the bases of which are combined with the collectors of the fourth and second transistors, the collector of the fifth transistor is connected to the collector of the first transistor, the emitters of the fourth and fifth transistors are connected to the second output of the second resistor.

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