KR860001638Y1 - Temperature-compensating bias circuit - Google Patents

Abstract

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Description

Bias Circuit for Temperature Compensation

1 is a configuration diagram of a conventional bias circuit for temperature compensation

2 is a block diagram of a bias circuit for temperature compensation of the present invention

3 is a configuration diagram of a multivibrator to which the bias circuit for temperature compensation of the present invention is applied.

4 is a signal waveform diagram for explaining the operation of the multivibrator

5 is a generation frequency characteristic diagram.

* Explanation of symbols for the main parts of the drawings

14,15,55: resistor 51,52: diode

70: bias circuit for temperature compensation

The present invention relates to a temperature compensation bias circuit that compensates for temperature drift of a transistor circuit, such as an emitter coupled unstable multivibrator.

In general, the operating characteristics of the transistor circuit vary with the change in the ambient temperature. Conventionally, in order to prevent the fluctuation | variation of the operating characteristic by this temperature drift, what kind of temperature compensation means is provided in a transistor circuit. For example, the power generation frequency of an emitter coupled type unstable multivibrator has a temperature drift. It has a temperature drift. In order to compensate for the ionic drift, the bias electron itself, which determines the power generation frequency of the mulberry vibrator, usually has a temperature drift. That is, a bias circuit is set, which gives temperature dependence to the bias voltage applied to the transistor circuit, and offsets the temperature drift of the multivibrator itself.

The circuit block diagram of the conventional temperature compensation bias circuit 60 of FIG. 1 is shown. The bias circuit 60 is a bias circuit for performing temperature compensation by using the decrease in the pure resistance of the diode as the temperature rises, and is connected to the resistors 14, 15 and the forward bias constituting the series circuit. Diodes 51... It consists of. The power supply voltage Vcc is connected to the resistor 14 which is one end of the series circuit, and the diode 51 of the other end is grounded. In addition, an output terminal 27 is provided between the resistors 14 and 15 in order to draw the voltage applied to the resistor 14 to the bias voltage V ₁ . This output terminal 27 is connected to a bias voltage input terminal of a transistor circuit (not shown) to perform temperature compensation.

The bias voltage V ₁ set by this conventional temperature correction bias circuit 60 is given by the following equation.

Here, R ₁₄ and R ₁₅ represent the resistance values of the resistors ₁₄ and ₁₅ , respectively, and V _D represents the forward voltage of the diode 51. At this time, the change rate with respect to the temperature T of the bias voltage V ₁ silver,

Is displayed.

In Equation (2), it can be seen that the bias voltage V ₁ set by the bias circuit 60 has a temperature drift.

As described above, by changing the bias voltage V ₁ according to the temperature, the temperature drift of the operating characteristics of the transistor determined by the bias voltage V ₁ is compensated for, but will be described in detail later. The temperature coefficient of the bias voltage V ₁ depends on the transistor circuit to which the bias circuit 60 is connected. Must match the value of, i.e. the temperature coefficient The value of must be one that can match any value.

However, temperature coefficient The value of is set by appropriately selecting the resistance values R ₁₄ and R ₁₅ and then manipulating the number n of diodes 51. Since n is an integer value, the temperature coefficient cannot take continuous values. You can't help it. Therefore, in the conventional temperature compensation bias circuit 60, it is difficult to match the temperature coefficient of a bias voltage to a desired value, and it had to set it to the approximation value. Therefore, complete temperature compensation cannot be performed and the temperature drift of the transistor circuit to which the bias circuit V ₁ is connected has not been eliminated. Therefore, in actually using the transistor circuit to which the temperature compensation bias circuit 60 is connected, since the operation characteristic still has a temperature drift, it is necessary to newly provide correction means for setting the obtained characteristic to be appropriate. This has become a big problem by increasing the price of increasing the circuit size.

An object of the present invention is to provide a temperature compensation bias circuit capable of performing a complete temperature compensation, which was not possible with a conventional temperature compensation bias circuit.

The present invention is a temperature compensation bias circuit having a configuration in which a plurality of diodes for temperature compensation are connected in series in a plurality of forward bias directions in parallel.

2 is a circuit diagram of the temperature compensation bias circuit 70, which is an embodiment of the present invention. The temperature compensating bias circuit 70 includes a resistor 53 and m diodes 52 in the conventional temperature compensating bias path shown in FIG. … The configuration is as if a series circuit is added in parallel.

That is, n diodes 51... … And a series circuit formed by connecting the series in series with a resistor 53 and m diodes 52. Are connected in parallel by aligning the directions of the diodes 51 and 52 so as to be forward biased when a voltage is applied. The resistor 14 is connected in series to one end of the parallel circuit 80 thus obtained, and the other end is grounded. The power supply voltage Vcc is connected to the resistor 14, and the output terminal 27 of the bias voltage V ₁ is provided at the intermediate point 50 of the resistor 14 and the parallel circuit 80.

When the bias voltage V ₂ set by the temperature compensation bias circuit 70 according to the above configuration is set to the potential of the intermediate point 50 as V ₂₇ ,

V ₂ = V _cc -V ₂₇ . … 3)

Is displayed. In addition,

Since the bias voltage V ₂ is

Obtained by Thus, the rate of change of temperature _B of bias voltage V ₂ silver,

Becomes

In the above formula (6), the temperature coefficient α of the bias voltage V ₂ is

It can be seen that. Therefore, by setting the resistance values R ₁₄ , R ₁₅ , and R ₅₃ to appropriate values, the temperature coefficient α can be matched to the desired value by manipulating the number n, m of the diodes 51 and 52.

As a result, temperature compensation of the transistor circuit to which the bias circuit 70 is connected can be performed completely.

Hereinafter, a detailed use example of the temperature compensation bias circuit 70 which is an embodiment of the present invention will be described in detail. As an example of the transistor circuit to which the bias circuit 70 is connected, an emitter coupled type unstable multivibrator used in an FM modulator of VTR is taken as an example.

3 is a circuit configuration diagram of the emitter coupled type unstable multivibrator 90 without using the temperature compensation bias circuit 70 according to the present invention. In addition, the part enclosed by the dotted line shows the bias circuit 28. As shown in FIG. The bias circuit 28 is a bias circuit without temperature compensation, and is composed of a series circuit formed by connecting the resistors 14 and 15 in series.

The resistor 14 is connected to the power supply voltage Vcc, and the resistor 15 is grounded. The bias voltage output terminal 27 is provided at the midpoint of the resistors 14 and 15.

The circuit configuration of the multivibrator 90 will be described below. The collectors of the pair of transistors 1 and 2 are connected to the emitters of the transistors 3 and 4, respectively. In addition, the collector of the transistor 1 is connected to the emitter of the transistor 5 together through the resistor 12. In addition, the collector of the transistor 1 is connected to the base of the transistor 2 via the base of the transistor 6 and the emitter coupling, and also to the base of the transistor 8, and the collector of the transistor 2, It is connected to the base of the transistor 1 via the base of the transistor 7 and the emitter coupling, and also to the base of the transistor 9.

The bases of the transistors 3 and 4 described above are commonly connected to the output terminal 27 of the bias circuit 28, and the collector is connected to the power supply voltage Vcc.

The base of the transistor 5, the collector, and the collectors of the transistors 6, 7, 8, and 9 are also connected to the power supply voltage Vcc. The emitter of the transistor 6 is connected to the base of the transistor 2 as described above, but is divided and grounded through the resistor 24. As such, the emitter of the transistor 7 is also divided and grounded through the resistor 25.

In addition, the emitters of the transistors 8 and 9 are connected to the bases of the transistors 10 and 11 through the resistors 20 and 22, respectively. The bases of the transistors 10 and 11 are grounded through the resistors 21 and 23, respectively, and the emitters are coupled to each other and grounded through the current source 17. The collectors of the transistors 10 and 11 are connected to the emitters of the transistors 1 and 2, respectively, and the emitters of the transistors 1 and 2 are coupled to each other via the capacitor 16. .

Next, the operation of the multivibrator 90 having the above-described configuration will be described with reference to the signal waveform diagram of FIG. In the following, the time shifts of the collector potentials V _C1 , V _C2 and the emitter potentials V _E1 , V _E2 of the transistors 1, 2 are followed.

In the power generation operation of the multivibrator 90, the transistors 1 and 2 alternately turn on and off in turn. At first, at time t ₁ , the transistor 1 ON ", considering the state in which the transistor 2 is turned off. At this time, since the transistor 3 is also "on", the collector potential V _C1 of the transistor 1 is a voltage V between the base and emitter V of the transistor 3 rather than the potential of the output terminal 27 of the bias circuit 28. _BE3 minute has become a low electric potential. When the output terminal 27 and the power supply voltage are set to V ₀ , the potential of the output terminal 27 is V _CC -V _0, so the collector potential V _C1 of the transistor ₁ at time t ₁ is

V _C1 = VCC -V ₀ -V _BE3 (t = t ₁ )

Becomes In the collector potential V _C2 of the transistor 2, since the transistor 2 is "off", the potential of only the voltage V _BE between the base and emitter of the transistor 5 is lower than the power supply voltage V _CC .

V _C1 = V _CC -V _BE5 (t = t ₁ )

Is displayed.

Next, emitter potentials V _E1 and V _E2 of the transistors ₁ and ₂ at time t ₁ are considered. Here, if the voltage between the base emitter of the transistor 7 is V _BE7 and the voltage between the base emitter of the transistor 1 in the "on" state is V _BE1 ,

V _E1 = V _CC -V _BE5 -V _BE5 -V _BE1 (t = t ₁ )

Becomes Therefore, since the transistor 1 is "on", the transistor 11 is also "on" and a constant current I ₀ flows through the capacitor 16 as indicated by the solid arrows in FIG. . As a result, the capacitor 19 is charged at a constant speed to the polarity in the direction of the arrow in the solid line, whereby the emitter potential V _E2 of the transistor 2 is, after the time t ₁ , as shown in FIG. Decreases at a constant rate. When the emitter potential V _E2 is reduced as it is and the base emitter voltage V _BE2 of the transistor 2 becomes a certain value, the state of the transistor 2 is inverted from "on" to "off".

When the value of the emitter voltage V _BE2 causing this inversion is set to V _BE2 (ON) and the time of inversion is t ₂ , the emitter potential V _E2 of the transistor ₂ at time t ₂ is

V _E2 = V _B2 -V _BE2 (ON) (t = t ₁ )

Becomes Since V _E2 is the base potential of the transistor 2 and V _B2 is only the voltage V _BE6 between the base and the emitter of the transistor 6 is better than the collector potential V _C1 of the transistor 1.

V _B2 = V _C1 -V _BE6 = V _CC -V ₀ -V _BE3 -V _BE6

Is displayed and eventually

V _E2 = V _CC -V _O -V _BE3 -V _BE6 -V _BE2 (ON) (t = t ₂ )

Obtained by

When transistor 2 is inverted from "off" to "on", transistor 1 is inverted from "on" to "off". Therefore, this time the collector potential V _C1 of the transistor (1)

V _C1 = V _CC -V _BE5 (t = t ₂ )

And the collector potential V _C2 of the transistor 2

V _C2 = V _CC -V _O -V _1BE4 (t = t2)

Becomes And emission at time t ₂ "on" the transistor 2 emitter voltage V _E2 is, as shown in the above grounds the emitter _E1 of the V at time t ₁ the transistor (2),

V _E2 = V _CC -V _BE5 -V _BE6 -V _1BE2 (t = t ₂ )

Becomes Here, V _BE2 represents the voltage between the base emitter of the transistor 2 in the " on " state. Thus, at time t ₂ , the emitter potential V _E2 of the transistor 2 is

V _CC -V _O -V _BE3 -V _BE6 -V _BE2 (ON)

in

V _CC -V _BE5 -V _BE6 -V _BE2

Up to, deducting and

V _O + V _BE3 -V _BE5 + V _BE2 (ON) -V _BE2

It is increasing. Here, when the transistor 3 is in the " on " state, the resistor 12 is selected so that the current flowing through each collector of the transistor 3 and the transistor 5 is the same, and the base of the transistor 3 The voltage V _BE5 between the emitter and the voltage V ₁ between the base and the emitter of the transistor 5 are the same. Therefore, the increase of the emitter low voltage V _E2 of the transistor ₂ at the time t _{2 described} above.

V _O + V _BE3 -V _BE5 + V _BE2 (ON) -V _BE2

Silver V _BE3 = V _BE5

Because of,

V _O + V _BE2 (ON) -V _BE2

Becomes The emitter of transistor (I) at time t ₂ emitter by the voltage V _E1 is in before time t ₂

V _CC -V _BE5 -V _BE7 -V _BE1

In the above increments only high potential,

V _E1 = V _CC -V _BE5 -V _BE7 -V _BE1 + V _O + V _BE2 (ON) -V _BE2 (t = t ₂ )

It can be seen that.

After the time t ₂ , in the state where the transistor I is "off" and the transistor 2 is "on", since the constant current I ₀ flows in the direction of the arrow of FIG. The emitter potential V _E1 of I) is lowered at a constant speed as shown in FIG. Then, if the voltage between the base and the emitter required for the transistor I to be turned "off" to "on" is V _BE1 (ON),

V _E1 = V _CC -V _BE5 -V _BE4 -V _BE7 -V _BE1 (ON)

At this point in time (time t ₃ ), the transistor I is turned on again and the transistor 2 is turned off. Emitter voltage V _E1 of transistor I in " on "

V _E1 = V _CC -V _BE5 -V _BE7 -V _BE1 (t = t ₃ )

Returning to, the increment of V _E1 at time t ₃ is

V _O + V _BE4 -V _BE5 + V _BE1 (ON) -V _BE1

to be. As described above, since the values of the resistors 13 are selected so that the voltages V _BE5 and V _BE5 between the transistors 4 and the base and emitters of the transistors 5 are the same, at last, V at time t ₃ . The increase in _E1 is

V _O + V _BE1 (ON) -V _BE1

Becomes As a result, the emitter voltage V _E2 of the transistor 2 at time t ₃ is equal to the time before time t ₃ .

V _CC -V _BE5 -V _BE6 -V _BE2

Higher than the above acid increments,

V _E2 = V _CC -V _BE5 -V _BE6 -V _BE2 + V _O + V _BE1 (ON) -V _BE1 (t = t3)

Becomes

Thereafter, the inversion of "on" and "off" of the transistors 1 and 2 is repeated, and the collector potential V _C1 of the transistor 1 or the collector potential V _C2 of the transistor 2 are respectively shown in FIG. As shown in (b), the pulse waveform is repeated at a constant cycle of 2T, so that the oscillation output of the multi-vibrator 90 is obtained. In this case, the terminal voltage of the capacitor 16 is in the period T rather than the change in the period T of the collector potential V _C1 of the transistor 1,

V _CC -V _O + V _BE4 -V _BE7 -V _BE1 (ON)

in

V _CC -V _BE5 -V _BE7 -V _BE1 + V _O + V _BE2 (ON) -V _BE2

Till,

2V _O + V _BE2 (ON) -V _BE1 + V _BE2 (ON) -V _BE2

Only changes. Here, by symmetrically selecting transistors 1 and 2,

V _BE1 = V _BE2 , V _BE1 (ON) = V _BE2 (ON)

Therefore, the change in the applied voltage of the capacitor 16 is

2 (V _O + V _BE1 (ON) -V _BE1 )

Becomes Therefore, when the capacity of the capacitor 16 is C,

C.2 (V _O + V _BE1 (ON) -V _BE1 ) = I ₀ .T

Is established, so the oscillation frequency f ₀ of the multivibrator 90 is

Obtained by Where V _C is the terminal voltage of the capacitor 16 when the " on "" off " of the transistors 1, 2 is generated.

V _C = V _O + V _BE2 (ON) -V _BE2 ... … (9)

Is displayed.

It can be seen that the oscillation frequency f ₀ changes by changing the constant current I ₀ in Equation (8). Therefore, the multivibrator 90 can be used as an FM modulator in the VTR by using the video signal as an input signal and changing the rectifying current I ₀ in phase with the input signal.

By the way, the oscillation frequency f ₀ of the emitter coupled type unstable multi-vibrator 90 has a temperature drift, but this will be described in detail below.

The reason why the oscillation frequency f ₀ has a temperature drift is that the condenser 16 terminal voltage V _C represented by the above formula (9) has a temperature drift. That is, for example, at the time t ₂ in which the transistor ₂ develops from "off" to "on", the collector currents of the transistors 1 and 2 are not actually the same, and thus, at time t ₂ . The loss occurs in the temperature coefficients of the emitter-base voltages V _BE1 and V _BE2 (ON) of the transistors 1 and 2, and the terminal voltage V _C has a temperature drift.

To know this in more detail, consider the collector current I _C2 (ON) flowing through the transistor ₂ at time t ₂ .

Now, when the transistor ₂ before time t ₂ is in the " off " state, the emitter potential V _C2 is It is assumed to be reduced. At this time, when the current flowing through the resistor 13 sets the mutual inductance of the transistor 2 to gm ² , Increases. Due to this, the collector potential V _C2 of the transistor 2 is Descend.

The change in the collector potential V _C2 passes through the base of the transistor 7, the transistor 1, the emitter junction, and the capacitor 16 in order, and returns the emitter of the transistor 2 itself as it is. The condition that the transistor 2 inverts from "off" to "on" means that the loop gain G at this time, that is,

Is more than one. Therefore, at the moment when G = 1 (time t2), the transistor 2 inverts from "off" to "on." At this moment, the collector current of the transistor 2 is I _O2 (ON), and the mutual inductance gm2 is

Is displayed. Where R is the Boltzmann constant, T is the absolute temperature, and q is the unit charge. In the above formulas (10) and (11), the collector current I _C2 (ON) at the time of inversion of the transistor 2 is

Obtained by

By the way, as described above, the collector current I _C2 (ON) is obtained, so that the base and emitter voltage V _BE2 (ON) of the transistor 2 at the time of inversion are the saturated currents of the transistors 1 and 2. If the value is I _S ,

Obtained by In addition, since the base-emitter voltage V _BE1 of the transistor 1 at the time of inversion, the collector current I _C1 of the transistor 1 is equal to I _O.

Obtained by Therefore, in the above formulas (13), (14) and (9), the terminal voltage V _C of the capacitor 16 at the time of power generation is

Obtained by From this, it became clear that the terminal voltage V _C became a function of the temperature T and had a negative temperature drift. Therefore, the oscillation frequency f ₀ represented by Formula (1) has a positive temperature drift.

By the way, it became clear that the temperature drift of the oscillation frequency f ₀ is due to the temperature drift of the terminal voltage V _C of the capacitor 16. Therefore, in order to compensate for the temperature drift of the oscillation frequency f _0, the temperature drift of the terminal voltage V _C represented by the above formula (15) may be compensated. Therefore, it is conceivable to provide a temperature drift to the base voltage V _O included in the formula (15) to offset the temperature drift of the terminal voltage V _C. When the base circuit 28 of FIG. 3 is replaced with the conventional base circuit 60 shown in FIG. 1, the bias voltage V _O becomes V ₁ according to Formula (1), and is represented by Formula (15). The terminal voltage V _C displayed is

Becomes Where the change to temperature T of V _C If you find,

Becomes And of formula (2) By substituting Is

Is saved. Resolving a temperature drift makes the value of said Formula (18) zero. Therefore, by setting the temperature TT ⁰ , determining the values of the resistances R ₁₄ and R ₁₅ and manipulating the value of the number n of the diodes 51, If so, the temperature lift at the oscillation frequency f ₀ disappears. However, as described above, Nn can only take an integer value, and in general, It is not always possible to set the value of to 0.

Therefore, when the bias circuit 70 of the present invention shown in FIG. 2 is replaced with the bias circuit 28, the terminal voltage V _C is

Become Is

Is obtained. Therefore, according to the present invention, the resistance values R ₁₄ , R ₁₅ , and R ₅₃ are selected as appropriate values, and then the two variables of the number n of diodes 51 and the number m of diodes 52 are operated independently, Formula (20) According to the value of the arbitrary temperature T _O, it is possible to "0".

Next, the effects of the present invention will be specifically described with reference to FIG. 5 is a temperature characteristic diagram with respect to the oscillation frequency of the multivibrator 90. This characteristic can select a value such as a resistance constituting the multibyte formatter 90 as follows.

Resistors 12, 13... 1.6 KΩ resistor 14... Ω

Resistance 15... 16 KΩ resistors 20, 22. 5.3KΩ

Resistors 21 and 23. 6 KΩ capacitor 16... 120 PF

Current source 17. 720 μA

The characteristic of FIG. 5A shows the case where the bias circuit 28 which does not have a temperature compensation effect as a bias circuit is connected to the multi-vibrator 90. As shown in FIG. As is apparent here, the oscillation frequency has a temperature drift, and the oscillation frequency fluctuates by 175KHZ in the temperature range of 0 ° C-100 ° C.

The characteristic of FIG. 5 (b) is the case where the conventional temperature compensation uses the bias circuit 60, and the number of diodes 51 is one, and the characteristic of (c) is two such cases. Indicates. In both of these characteristics, it can be seen that the temperature drift of the oscillation frequency is reduced, but there are still variations of 68 KHZ in (b) and 83 KHZ in (c). Also, the change in quantum characteristics is opposite, (b) the oscillation frequency increases with temperature rise, and (c) decreases conversely. Therefore, in this result, the most suitable number of diodes 51 can be found to be between "1 or 2", but the number can take only an integer value, and the temperature is higher than that used in the conventional bias circuit 60. You cannot expect a reward.

The characteristic of FIG. 5 (d) shows a case where the bias circuit 70 of the present invention is used. At this time, the resistors 14, 15, and 53 are selected as 500Ω, 11.3KΩ, and 8.7KΩ, respectively. The number n of diodes 51 is two, and the number m of die modes 52 is one.

By using the temperature compensation bias circuit 70 of the present invention, the temperature dependence of the oscillation frequency is almost eliminated, and suppressed by a variation of only 16 KHZ in the range of 0 ° C-100 ° C.

As described above, the temperature compensation bias circuit 70 of the present invention is simple in construction and has a very large effect.

Claims (1)

In a temperature compensation bias circuit having a circuit composed of a (correction) resistor and a plurality of series-connected diodes connected between the power supply and ground, n diodes 51 are serially connected to the first resistor 15. The first series circuit configured by connecting to the second resistor 53 is connected in series with the m diodes 52 in series, and the second series circuit configured by connecting in parallel with the first series circuit. And a third resistor 14 connected to one end of the parallel circuit composed of the first and second series circuits and connected to the other end or grounded, and the other end of the vapor phase parallel circuit being grounded. Alternatively, the diodes 51 and 52 are connected to a power source and are arranged in the same direction and in a forward biased direction, and the output terminal 27 is provided at the connection point of the third resistor 14 and the parallel circuit. Temperature compensation, characterized in that Bias circuit.