JPS6031124B2 - Arithmetic amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an arithmetic multiplier in which a differential amplifier including transistors and a multiplier in which a phase compensation capacitor is connected between the input side and the output side are connected in cascade. Concerning the improvement of utensils.

As shown in FIG. 1, the basic structure of this type of operational multiplier includes, for example, two NPN type transistors QI and Q2, and the collectors of the transistors QI and Q2 are connected to a load, for example, through which DC current can pass. The emitters are connected to the power supply connection terminal la through the resistors RI and R2, and the emitters are connected to the power supply connection terminal lb, which is paired with the power supply connection terminal la, respectively;
The differential amplifier 3 has a configuration in which the input terminals 2a and 2b are led out from the bases of the transistors QI and Q2, respectively, and the output terminal 2c is led out from the collector of one of the transistors QI and Q2, for example, the collector of the transistor Q2. and, for example, one PNP type transistor Q3, the emitter of which is directly connected to the power supply trailing terminal 4a, the collector of which is connected to the power supply terminal 4b through a load capable of passing direct current, such as a resistor R3, and the base and collector of which are connected to the power supply terminal 4b, respectively. Input terminal 5
a and a multiplier 6 having a configuration in which the output terminal 5c is led out, and the power supply connection terminal la of the differential multiplier 3
The power supply connection terminal 4a of the multiplier 6 is connected to the positive polarity side terminal 8a of the power supply 7, and the power supply connection terminal lb of the differential multiplier 3 and the power supply connection terminal 4b of the multiplier 6 are connected to the negative polarity side of the power supply 7. terminal 8b of
The output terminal 2c of the differential multiplier 3 is connected to the input terminal 5a of the multiplier 6, while a phase compensation capacitor 9 is connected between the input side and the output side of the multiplier 6. Furthermore, the input terminals 2a and 2b of the differential multiplier 3 are connected to input terminals 10a and 10b as operational multipliers, respectively, and the output terminal 5c of the multiplier 6 is connected to output terminal 1 as an operational multiplier.
It has a configuration in which 0c can be derived respectively.

Moreover, an operational intensifier with such a principle configuration has a certain frequency (
In the following range (denoted as fc), the differential amplifier driven at a constant current operates as a transconductance amplifier that converts the differential input voltage into collector current, so the transconductance of the differential amplifier 3 is gm, differential multiplier 3
When the current flowing through the power supply connection terminal lb is 13, the current gain of the multiplier 6 is a6, and the value of the load connected to the output terminal 10c is RL, then A, = gm・86・RL・……”[ 11
gm=q. 13/k・T………………■ (where q is the electron charge, k is Polzmann's constant, and T is the ambient temperature of the differential multiplier 3 expressed in absolute temperature). has a high voltage gain value A, and has a frequency f
For frequencies above fc, frequencies above fc are generally fm
And when the capacitance of the phase compensation capacitor 9 is C9, the value of the voltage gain that decreases linearly as the frequency fm increases, expressed as fm/2 fmC9...[3-] It exhibits a frequency f-voltage gain A characteristic as shown in FIG.

By the way, such arithmetic multipliers are used as circuit elements in various arithmetic devices, but the manner in which they are used is when they are used in a frequency range below frequency fc, as seen in the frequency-voltage gain characteristics shown in Fig. 2. When used in a frequency range above frequency fc, there are cases where it is used across both the range below frequency fc and above fc, and regardless of which frequency range it is used, the voltage of power supply 7 It is also desirable to be able to obtain a voltage gain that is independent of changes in ambient temperature.

However, if the voltage of the power supply 7 changes, the value of 13 changes accordingly, and if the ambient temperature of the differential multiplier 3 changes, the value of T changes accordingly, and the voltage gain The value of A is '1
} and '3', the value of the voltage gain A depends on the gm given by the equation This will depend on the change in the outside temperature in step 3.

In particular, when the operational amplifier is used in a frequency range above frequency fc or in a frequency range that includes this range, a change in the value A2 of voltage gain A expressed by equation '3' poses a problem. Note that the power supply 7 with the value A of the voltage gain A expressed by the formula 1}
The variation with respect to the voltage of the voltage and the ambient temperature of the differential multiplier 3 is the value A of the voltage gain A, which itself has a relatively large value. Since the term affected by changes in the power supply voltage and ambient temperature in terms of characteristics has a relationship in which the voltage gain A of the operational amplifier is used as the denominator, this is not as much of a problem. For this reason, various proposals have been made in the past to compensate for the fact that the value of the voltage gain A expressed by the glue equation does not depend on the voltage of the power supply 7 and the outer temperature of the differential multiplier 3. It still wasn't something I was satisfied with.

In view of the above, the present invention particularly provides a value A2 of the voltage gain A mentioned above.
The purpose of the present invention is to propose such an operational multiplier that effectively compensates for the dependence of the voltage on the power supply 7 and the ambient temperature of the differential multiplier 3. Since the value of the mutual conductance gm is proportional to the value of the current 13 mentioned above, and inversely proportional to the value of the temperature T mentioned above, the value of the current 13 is made to be independent of the voltage change of the power supply 7. If the value of the current 13 is increased by the amount that the value of the mutual conductance gm decreases as the value of the temperature T increases, the value of the mutual conductance gm will change depending on the voltage of the power supply 7 and the differential multiplier 3.
can compensate for changes in the ambient temperature of g, and thus g
It is noted that if the value of m is compensated, the value A2 of the voltage gain A can compensate for changes in the voltage of the power supply 7 and the external temperature of the differential multiplier 3. As will become clear from the detailed description of the embodiments of the present invention with regard to the figures, in FIG. 3, corresponding parts to those in FIG. For example one PN
It has a P-type transistor Q4, the collector and emitter of which are connected to power supply connection terminals 21a and 21b, respectively,
Further, a constant current circuit 23 having a control terminal 22 led out from the base is provided, and the constant current circuit 23 connects the power supply connection terminals 21a and 21b to the power supply connection terminals lb and 21b of the differential multiplier 3, respectively. It is inserted between the power supply connection terminal lb of the reed action multiplier 3 and the terminal 8b of the power supply 7 so as to be connected to the terminal 8b of the power supply 7.

For example, two PNP transistors Q5 and Q6 and 1
the emitter of the transistor Q5 is directly connected to the power supply connection terminal 24a, the base is connected to the power supply connection terminal 24a through the resistor 25, and directly connected to the emitter of the transistor Q6; The collector is directly connected to the base of the transistor Q6, and is connected to the power supply connection terminal 24b that is paired with the power supply connection terminal 24a through the DC load 26, and the collector of the transistor Q6 is directly connected to the base of the transistor Q7. A control circuit 29 is provided, which is connected to the collector of the transistor Q7 through the resistor 27, further has the emitter of the transistor Q7 directly connected to the power supply terminal 24b, and has an output terminal 28 led out from the collector. Power terminals 24a and 24b of the lever control circuit 29
are connected to terminals 8a and 8b of power supply 7, respectively, and output terminal 28 is connected to control terminal 22 of constant current circuit 23, respectively. In this case, the DC load 26 is a saddle-type field effect transistor 30 whose one connection terminal is connected to the source, and whose gate and drain are connected to each other so that the other output terminal can be led out.
can be applied. The above is an example of the configuration of the present invention. In such a configuration, the power supply connection terminal lb of the differential multiplier 3 is connected to the terminal 8b of the power supply 7 through the constant current circuit 23 instead of being connected directly to the terminal 8b of the power supply 7, On the other hand, since it is the same as the case in FIG. 1 except that the constant current circuit 23 is controlled by the control circuit 29, the above-mentioned frequency-voltage in FIG. It is clear that a gain characteristic can be obtained, but the current 13' flowing to the power supply connection terminal lb of the differential amplifier 3, the reverse saturation current of the transistor Q4 applied by the constant current circuit 23, is ls4, and the transistor Q4 is
When the voltage applied between the base and emitter of is V4, -3: IS4eXp (k level V4).・・・．・・・．
It is given by...

In this case, V4 is equal to the voltage obtained between the output terminal 28 of the control circuit 29 and hence the collector of the transistor Q7 and the power supply connection terminal 8b, V7 is the voltage applied between the base and emitter of the transistor Q7, and L is the collector current of the transistor Q6. , if the value of the resistor 27 is R7 and the base current of the transistor Q7 is ignored (this base current is k
'It is sufficiently small compared to this so it can be ignored), V4; V7-
R completed・16. ．．・．． ．．・．． ．．・・・・・・．・It is given by the formula [5}, while 16 is the reverse saturation current of the transistor Q7 IS? If so, IS7eXp (k old/V7).・・・
．．・…． ..., but if the base-emitter voltage of transistor Q5 is VBE5, the value of resistor 25 is R5, and the base current of transistor Q6 is ignored (this base current is sufficiently small compared to ), L=VBE5/R5......{
7), so by substituting equation [7} into equation (5), V4 is V4=V7-Turtle VB song-----------
‐‐‐‐{8' is given.

Therefore, if we solve equation {4) for 13 using equations (6-, [7} and ■) (however, IS4 = ls7),
ln13ilnVBE5-unit-VBE5-reception-lnR5
‐‐‐.... ...'91 (here, ln represents the natural logarithm) is obtained.

Therefore, the current 13' flowing through the power supply terminal lb of the differential multiplier 3
Although it depends on the ambient temperature T, it is unrelated to changes in the voltage of the power supply 7. At the place, the outdoor temperature T
Looking at the dependence on T, if we differentiate equation [9} with respect to T, we get ÷. The following relationship is obtained: d13-, 3dT-point, d-equivalent cost-Toru, Mizojutsutsu, Tai (Ning, etc.) skin side, and the first term on the right side of the rigid equation is the temperature of the base-emitter voltage VBE5 of transistor Q5. coefficient and therefore generally takes a negative value, and the second term is due to the resistance 2
5, and the temperature coefficient of the resistor 25 is sufficiently smaller than the absolute value of the temperature coefficient of the base-emitter voltage VB85 of the transistor Q5 when the resistor 25 is formed by diffusing impurities into the semiconductor substrate. exhibits a positive value with an absolute value, and therefore the first and second on the right side of the dish equation
The value due to the term is negative, while the third term in equation [10} is always a positive value, so if the ratio of R7/R5 is chosen appropriately, the current 13' will have a positive temperature with respect to the outer sphere temperature T. This results in a dependence with a coefficient.

If this relationship is plotted against temperature T using the value of the ratio R7/R5 as a parameter, it will be as shown in FIG. 4. Therefore, if the value of the ratio of R7/R5 is appropriately selected so as to obtain a curve as shown by the symbol M in the curve shown in FIG.
In the range Ta to Tb, the value of the current 13 increases as the ambient temperature T increases, and therefore, based on the above equation (2), the value of the current 13 increases as the ambient temperature T increases. Although the mutual conductance gm of vessel 3 becomes small, gm becomes large as 13 becomes large, and in the end gm remains approximately constant within the range of change even if the ambient temperature T of Ta to Tb changes. be.

As described above, according to the exemplary configuration of the present invention described above, the value of the mutual conductance gm of the differential multiplier 3 compensates for changes in the voltage of the power supply 7 and the temperature outside the differential multiplier 3. Therefore, in particular, the value of the voltage gain A expressed by the above-mentioned equation '3) is an arithmetic intensifier that can compensate for changes in the voltage of the power supply 7 and the outer atmosphere temperature of the differential intensifier 3. It has great features that will be obtained.

The above description merely shows one example of the present invention, and the configurations of the differential multiplier 3, the multiplier 6, the constant current circuit 23, and the control circuit 29 are not limited to those shown in the drawings. Based on the configuration shown, various modifications and changes can be made from this configuration.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing an example of an operational amplifier that is the basis of the present invention, FIG. 2 is a diagram showing the frequency-voltage gain characteristics of the operational amplifier used to explain the present invention, and FIG. FIG. 4 is a connection diagram showing an example of the operational multiplier according to the invention, and FIG. 4 is a curve diagram showing the relationship between the current flowing through the power supply terminal of the differential multiplier with respect to the outer atmosphere temperature, to provide an explanation thereof. In the figure, QI to Q7 are transistors, la and lb are power supply connection terminals, 2a and 2b are input terminals, 3 is a differential amplifier, and 6
is an intensifier, 7 is a power supply, 9 is a phase compensation capacitor, 23
2 shows a constant current circuit, and 29 shows a control circuit. Figure 2 Figure 4 Figure Ship Figure 3

Claims (1)

[Claims] 1 A differential amplifier including transistors and an amplifier including a phase compensation capacitor connected between the input side and the output side are connected in cascade, and the transistors of the differential amplifier are driven with a constant current. In an operational amplifier in which a constant current circuit is inserted in series with a power supply, and a current flowing through the constant current circuit is controlled by a control circuit, the control circuit includes a resistor and a transistor connected to the power supply, and the constant current It consists of a cascade connection of a first circuit whose temperature coefficient is positive and a second circuit whose temperature coefficient of the constant current circuit is negative, and the value of the resistance included in the first circuit and the second circuit are connected in series.
An operational amplifier, characterized in that a ratio between the value of the resistor included in the circuit and the temperature coefficient of the transfer conductance of the differential amplifier is set to zero.