RU2488874C1 - Source of reference voltage determined through energy gap doubled width - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: device contains five transistors, three resistors and a current source which is placed between the power supply bus and the output terminal; the first and the second resistors, via their first outputs, are connected to the output terminal; the bases of the first and the second transistors are connected to the collectors of the first and the fifth transistors; the third resistor is placed between the common bus and the second transistor emitter; the emitters of the first and the third transistors are connected to the common bus; the collector of the third transistor is connected to the output terminal; the bases of the third, the fourth and the fifth transistors are connected to the collectors of the second and the fourth transistors; the emitter of the fourth transistor is connected second output of the second resistor; the emitter of the fifth transistor is connected to the second output of the first resistor.

EFFECT: obtainment of thermally stable output voltage at values closed to doubled energy gad width.

3 dwg

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 disadvantage of which is the 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. 3.27], 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 alleged 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, in the prototype circuit containing the first and second resistors connected by the first leads to the output terminal, the first and second transistors, the bases of which are connected to the collector of the first transistor, the third resistor connected between the common bus and the emitter of the second transistor, the third transistor, the base of which is connected to the collector of the second transistor, a current source connected between the power bus and the output terminal, the emitters of the first and third transistors are connected to a common bus, to the lecturer 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 second and fourth transistors, the emitter of the fourth transistor is connected to the second terminal of the second resistor, the emitter of the fifth transistor is connected to the second terminal of the first resistor, the collector of the fifth transistor is connected to the collector first transistor.

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, and three resistors (first to third), indicated, respectively, by the numbers 6, 7 and 8 and the current source 9 connected between the power bus and the output terminal, resistors 6 and 7 are connected by the first conclusions to the output terminal, the bases of transistors 1 and 2 are connected to the collectors of transistors 1 and 5, the resistor 8 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 collector of transistor 3 is connected to the output hydrochloric terminal bases of transistors 3, 4 and 5 are connected to the collectors of the transistors 2 and 4, the emitter of the transistor 4 is connected to the second terminal of the resistor 7, the emitter of transistor 5 is connected to the second terminal of the resistor 6.

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 the} transistor VT3 and the voltage drop U2 on the resistor R2, which can be described by the following expression:

$$U_{\mathrm{at}sx}=U_{b\mathrm{uh}3}+U_2={\phi }_T\ln \frac{I_3}{I_S}+R_2{I}_2\approx 0.6+R_2{I}_2,(\mathrm{one})$$

where φ _T ≈26 mV is the temperature potential; 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 transistors VT1 and VT2 and the voltage drop U ₃ on the resistor R3, writing the expression:

U ₃ = U _be1 -U _be2 ,

or $$R_3{I}_2={\varphi }_T\ln \frac{I_{\mathrm{one}}}{I_S}-{\varphi }_T\ln \frac{I_2}{N{I}_S}={\varphi }_T\ln \frac{N{I}_{\mathrm{one}}}{I_2}\approx {\varphi }_T\ln N,(2)$$

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 emitter areas 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

$$I_2=\frac{{\varphi }_T\ln N}{R_3}.(3)$$

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

$$d{I}_2=\frac{\ln N}{R_3}d{\varphi }_T=\frac{{\varphi }_T\ln N}{R_3}\frac{dT}{T}=I_2\frac{dT}{T},(\mathrm{four})$$

where φ _T = kT / q; k is the Boltzmann constant; T is the absolute temperature; q is the electron charge.

Differentiating expression (1), we obtain

$$d{U}_{\mathrm{at}sx}=R_{2}d{I}_2+d{U}_{b\mathrm{uh}3}.(5)$$

To find the increment dU _be3 , the dependence

$$I_S=C{T}^3\exp \left(-E/{\varphi }_T\right),(6)$$

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), is reduced to the form

$$d{U}_{\mathrm{at}sx}=\left(U_{\mathrm{at}sx}-3{\varphi }_T-E\right)\frac{dT}{T}+{\varphi }_T\frac{d{I}_3}{I_3}.(7)$$

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

$$U_{\mathrm{at}sx}=3{\varphi }_T+E.(8)$$

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 for equal currents I ₁ , I ₂ , I ₃ , and the approximate equality of the increments dI ₁ and dI ₂ , s taking into account (4), we obtain

$$\frac{d{I}_3}{I_3}\approx -2{\varphi }_T\frac{dT}{T}.(9)$$

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

$$d{U}_{\mathrm{at}sx}\approx \left(U_{\mathrm{at}sx}-\left(2{\varphi }_T+E\right)-3{\varphi }_T\right)\frac{dT}{T}.(10)$$

The operation of the claimed device is similar to the work of the Vidlar diode (figure 1). However, the equality of the currents of transistors 1 and 2 (Fig. 2) is already provided more accurately by the current follower on transistors 4, 5 and resistors 6, 7. 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:

$$U_{\mathrm{at}sx}=R_7{I}_2+{\varphi }_T\ln \frac{I_2}{I_S}+{\varphi }_T\ln \frac{I_3}{I_S},(\mathrm{eleven})$$

where R ₇ is the resistance of the resistor 7; I ₂ and I ₃ are the emitter currents of transistors 4 and 3, respectively.

The current I ₂ is equal to the current I _{1 of the} emitter of the transistor 1 and is determined by the expression:

$$I_2=\frac{{\varphi }_T\ln N}{R_8},(12)$$

where R ₈ is the resistance of the resistor 8; N is the ratio of the emitter areas of transistors 2 and 1.

Differentiating expression (12), we can derive the equalities:

$$\frac{d{I}_{\mathrm{one}}}{I_{\mathrm{one}}}=\frac{d{I}_2}{I_2}=\frac{dT}{T}.(13)$$

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

$$d{U}_{\mathrm{at}sx}=\left(U_{\mathrm{at}sx}-6{\varphi }_T-2E\right)\frac{dT}{T}+{\varphi }_T\frac{d{I}_2}{I_2}+{\varphi }_T\frac{d{I}_3}{I_3}.(\mathrm{fourteen})$$

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

$$d{U}_{\mathrm{at}sx}=\left(U_{\mathrm{at}sx}-2\left(2{\varphi }_T+E\right)-3{\varphi }_T\right)\frac{dT}{T}.(\mathrm{fifteen})$$

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

$$\Delta U_{\mathrm{at}sx}=3{\varphi }_T\frac{\Delta T}{T}.(16)$$

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 (out1) and the inventive device (out2) on temperature. At the same time, for convenience of comparison, the voltage out1 is increased by 1.132B. 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 stabilizer containing the first and second resistors connected by the first terminals to the output terminal, the first and second transistors, the bases of which are connected to the collector of the first transistor, the third resistor connected between the common bus and the emitter of the second transistor, the third transistor, the base of which is connected to the collector of the second a transistor, a current source connected between the power bus and the output terminal, the emitters of the first and third transistors are connected to a common bus, the collector of the third transistor is connected to the output the bottom terminal, characterized in that the fourth and fifth transistors are introduced, the bases of which are connected to the collectors of the second and fourth transistors, the emitter of the fourth transistor is connected to the second terminal of the second resistor, the emitter of the fifth transistor is connected to the second terminal of the first resistor, the collector of the fifth transistor is connected to the collector of the first transistor.

Images