JPH04334106A - Integrated differential signal circuit - Google Patents

Abstract

PURPOSE:To prevent a deviation in an offset caused by a change in ambient temperature. CONSTITUTION:An output of a constant current source 11 is connected to a collector of a drive transistor (TR) Q15. An emitter of a 1st TRQ21 is connected to a collector of a 1st follower TR Q11 being a component of a current mirror circuit 12, an input signal is given to its base, an emitter of a 2nd TRQ22 is connected to a collector of a 2nd follower TRQ12 and an input signal is led to its base. The relation of aapprox.=b/c is established, where (a) is a temperature characteristic of the current source 11, (c) is a temperature characteristic of a variable resistor VR varying a ratio of collector currents of the two follower TRs Q11, Q12 and (b) is a temperature characteristic proportional to the absolute temperature.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog integrated circuit, and more particularly to an integrated differential signal circuit whose offset is adjusted by a variable resistor as an external element.

0002

2. Description of the Related Art As shown in FIG. 5, the input section of an integrated differential amplifier circuit consists of three transistors Q91 to
A current mirror circuit is configured by Q93, and the current value of the current mirror circuit is set by a constant current source 91. A configuration is adopted in which input signals are guided to the emitters of the transistors Q94 and Q95, and input signals are applied to input terminals 94 and 95, which are the bases of these transistors Q94 and Q95. By applying a positive power supply P91 to the emitters of transistors Q92 and Q93 via a variable resistor VR91, which is an external element,
With equal voltages applied to the input terminals 94 and 95, offset adjustment was performed using a variable resistor VR91 so that a specified voltage appeared at the output terminal of the circuit to which the outputs 96 of the transistors Q94 and Q95 were led.

0003

[Problem to be Solved by the Invention] Since the temperature characteristics of the constant current source 91 in the above configuration are set independently of the temperature characteristics of the variable resistor VR91, for example, the output value does not change at a certain environmental temperature. After offset adjustment is performed to obtain the specified voltage, if the environmental temperature changes, the resistance values between terminals 97 and 98 of variable resistor VR91 will differ (generally, these resistance values are changed for offset adjustment). are rarely equal), therefore, a difference occurs in the voltage variation between these terminals 97 and 98 due to temperature change (the voltage variation between the terminals with a large resistance value becomes larger). As a result, the ratio of the current value applied to the emitter of transistor Q92 and the current value applied to the emitter of transistor Q93 changes, and even though offset adjustment has already been performed, the output terminal is There was a problem that a new offset voltage was generated.

The present invention was conceived to solve the above problems, and its purpose is to provide an integrated differential signal circuit that can prevent offset shift due to changes in environmental temperature. It is in.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, a differential signal circuit formed into an integrated circuit according to the present invention has one of a pair of power supply terminals as a first power supply terminal and the other as a second power supply terminal. In addition, when the transistor to which the current is input in the current mirror circuit is the drive transistor,
A constant current source whose output is connected to the collector of the drive transistor, and a pair of transistors provided corresponding to the pair of outputs of the current mirror circuit, the bases of which are connected to the base of the drive transistor, 1st
A pair of driven transistors whose emitters are supplied with current from a power supply terminal, and when one of the pair of driven transistors is used as a first driven transistor and the other as a second driven transistor, a first transistor whose emitter is connected to the collector thereof, whose collector is connected to a second power supply terminal, whose emitter is connected to the collector of a first transistor whose base receives an input signal, and whose emitter is connected to the collector of a second driven transistor; A second power supply terminal is connected to the collector thereof, and a second transistor is connected to the base thereof to which an input signal is introduced, and the emitter of at least one of the first and second driven transistors is connected to the second transistor. Let c be the temperature characteristic of a variable resistor, which is an external element whose terminal is connected and which changes the ratio of the collector current of the first driven transistor to the collector current of the second driven transistor, and let a be the temperature characteristic of the constant current source. , where b is the temperature characteristic proportional to the absolute temperature, the temperature characteristic a of the constant current source is set to a value such that a≈b/c. Further, when a pair of transistors each having an emitter connected to a constant current source and an input signal guided to each base is used, one of the pair of transistors is used as a first transistor, and the other is used as a second transistor. , a third transistor whose collector and base are connected to the collector of the first transistor, whose collector is connected to the collector of the second transistor, and whose base is connected to the base of the third transistor. 4 transistors, the terminal of which is connected to the emitter of at least one of the third and fourth transistors, and the ratio of the collector current of the third transistor to the collector current of the fourth transistor is When the temperature characteristic of the variable resistor, which is an external element to be changed, is f, the temperature characteristic of the constant current source is d, and the temperature characteristic proportional to absolute temperature is e, the temperature characteristic d of the constant current source is d≒
The value is e/f.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing the electrical configuration of a first embodiment of the invention.

In the figure, the emitter of a drive transistor Q15, which is a transistor that constitutes an input section in the current mirror circuit 12, and the emitter of a first driven transistor Q11, which is one of a pair of transistors that constitute an output section of the current mirror circuit 12. , and the emitters of the driven transistor Q13 are connected to the first power supply terminal P11 where a positive voltage appears, and the emitter of the second driven transistor Q12 paired with the first driven transistor Q11 is connected to the , and is led to one terminal of an externally provided variable resistor VR11, and the other terminal of this variable resistor VR11 is connected to a first power supply terminal P11.

The base of the drive transistor Q15, the first
The bases of the second driven transistors Q11 and Q12 and the base of the driven transistor Q13 are connected to each other, and the emitter of the transistor Q14 is led to the base of the driving transistor Q15. The collector of the drive transistor Q15 is connected to the base of the transistor Q14 and one output of the constant current source 11, and the collector of the transistor Q14 and the other output of the constant current source 11 are connected to a second ground terminal. It is led to the power supply terminal G11.

The collector of the first driven transistor Q11 is led to the emitter of the first transistor Q21 and the base of the transistor Q16, and the base of the first transistor Q21 is connected to the input terminal 13, The collector of Q21 is led to the second power supply terminal G11. The collector of the second driven transistor Q12 is connected to the emitter of the second transistor Q22 and the base of the transistor Q17, the base of the second transistor Q22 is led to the input terminal 14, and the collector is connected to the second power supply. Connected to terminal G11. The collector of transistor Q13 is connected to the emitters of both transistors Q16 and Q17, and the collector of transistor Q16 and the collector of transistor Q17 are sent to a circuit following the next stage (not shown).

In the above configuration, the emitter areas of the drive transistor Q15, the first driven transistor Q11, and the driven transistor Q13 are equal to each other;
The emitter area of the second driven transistor Q12 is twice the emitter area of these transistors Q11, Q13, and Q15.

Further, the temperature characteristic of the constant current source 11 is a, the temperature characteristic proportional to the absolute temperature is b, and the variable resistor VR1
If the temperature characteristic of 1 is c, then these relationships are set to be a≈b/c.

The operation of the first embodiment, the configuration of which has been explained above, will be explained below.

First and third driven transistors Q11
, Q13 operate as a current mirror of the drive transistor Q15, so a current equal to the current flowing through the constant current source 11 is output to their collectors (the transistor Q14 reduces errors caused by the influence of the base current). (provided for). Furthermore, the emitter area of the second driven transistor Q12 is
Since it is twice that of the other transistors Q11, Q13, and Q15 constituting the current mirror circuit 12, when a current approximately equal to that of the constant current source 11 is output to its collector, the base-emitter voltage is Since it is smaller than that of the other transistors Q11, Q13, and Q15, the difference is provided by the variable resistor VR11.

The first transistor Q21, whose emitter is supplied with current by the above operation, operates as an emitter follower, and the signal applied to the input terminal 13 is guided to the base of the transistor Q16 as a low impedance signal. The same applies to the second transistor Q22, and the signal applied to the input terminal 14 is guided to the base of the transistor Q17. Since the pair of transistors Q16 and Q17 operate as a differential amplifier, the outputs 16 and 17 have input terminals 13 and 1.
The difference between the signals given to 4 is amplified and appears.

Now, equal voltages are applied to the pair of input terminals 13 and 14, and the variable resistor VR11 is connected so that the voltage at the output terminal of the circuit following the next stage to which the outputs 16 and 17 are led becomes a specified voltage. It is assumed that the offset adjustment has been completed.

As already explained, since the normal temperature is a little less than 300°K, the value b indicating temperature characteristics proportional to absolute temperature is: b = 1/300 = 3333 ≒ 3400
ppm, and the temperature characteristic c is c = -300 ppm since a carbon resistor is used as the variable resistor VR11. Further, the temperature characteristic a of the constant current source 11 is a≒ b /
Since it is set to be c, a≒ (1+0.0034) / (1-0.0003
)≒ 1 + 0.0034 + 0.0003= 1
+0.0037, and its temperature characteristic a is 3700 ppm.

Therefore, the temperature characteristic of the current when looking from the emitter of the first transistor Q21 to the collector of the first driven transistor Q11 is the same as the temperature characteristic of the constant current source 11, and its value is 3700 ppm.

Furthermore, the temperature characteristic of the second driven transistor Q12 with respect to the voltage between the base and emitter is proportional to the absolute temperature, so its value is 3400 ppm.
(The influence of the change in current can be ignored since it is logarithmic), and the variable resistor V
Regarding the temperature characteristic y of the voltage between both terminals of R11, y = a × c = (b / c) × c = b, which is equal to the temperature characteristic of the voltage between the base and emitter of the second driven transistor Q12. , variable resistor V
Since it is possible to ignore that R11 is connected to the emitter, the temperature characteristics of the current when looking from the second transistor Q22 to the collector of the second driven transistor Q12 are as follows: Q
3700pp, which is equal to the temperature characteristic of the collector current of 11
m, and the first and second driven transistors Q11
, Q12 have the same temperature characteristics.

FIG. 2 is a circuit diagram showing the electrical configuration of a second embodiment of the invention.

Since this embodiment has substantially the same structure as the embodiment shown in FIG. 1, only the different parts will be explained, and the same parts will be designated by the same reference numerals as in FIG. A reference numeral will be given, and a description of the configuration will be omitted.

One end terminal T11 of a variable resistor VR12, which is an external element, is connected to the emitter of the first driven transistor Q11.
The other end terminal T13 of the variable resistor VR12 is connected to the emitter of the variable resistor VR12. The sliding terminal T12 of this variable resistor VR12 is connected to the first power terminal P.
11 are connected. Further, the emitter area of the second driven transistor Q12a is the same as that of the first driven transistor Q12a.
It is equal to the emitter area of 11. The other parts are the same as the configuration shown in FIG. 1, and the temperature characteristic of the constant current source 11 is a, and the temperature characteristic of the variable resistor VR12 is c.

The operation of the second embodiment will be explained below.

Temperature characteristics of the collector current of the first driven transistor Q11 and the temperature characteristics of the second driven transistor Q1
Regarding the temperature characteristics of the collector current of terminal T11
and the temperature characteristics of the voltage between the terminal T12 and the terminal T12, and the temperature characteristics of the voltage between the terminal T12 and the terminal T13,
As already explained, since both have temperature characteristics (value b) proportional to the absolute temperature, the sliding terminal T of the variable resistor VR12
No matter where the position of the constant current source 11 is set, the temperature characteristics are the same, and the value thereof is 3700 ppm, which is equal to the temperature characteristic of the current of the constant current source 11.

FIG. 3 is a circuit diagram showing the electrical configuration of the first embodiment according to the second aspect of the invention.

In the figure, a positive power supply P31 is connected to one terminal of each of the constant current source 33 and the constant current source 34, and the other terminal of the constant current source 33 is connected to the first and second transistors Q31. , Q32. Also, the first transistor Q31
The base of the second transistor Q32 is connected to the input terminal 31, and the base of the second transistor Q32 is led to the input terminal 32. The collector of the first transistor Q31 is connected to the collector and base of the third transistor Q33, and to the collector and base of the fourth transistor Q33.
The collector of the second transistor Q32 is connected to the collector of the fourth transistor Q34 and the base of the transistor Q35.

The emitter of the third transistor Q33 is led to one end terminal T31 of an externally provided variable resistor VR31, and the emitter of the fourth transistor Q34
The emitter of is connected to the other end terminal T33 of variable resistor VR31, and the sliding terminal T32 of variable resistor VR31 is grounded. The other terminal of the constant current source 34 is connected to the transistor Q35.
The emitter of transistor Q35 is grounded. and transistor Q35
An output 35 is sent from the collector to a subsequent circuit (not shown).

In the above configuration, if the temperature characteristic of the constant current source 11 is d, the temperature characteristic proportional to the absolute temperature is e, and the temperature characteristic of the variable resistor VR11 is f, then the relationship between these is d≈e/ f.

The operation of the first embodiment, the configuration of which has been explained above, will be described below.

[0029] First to fourth four transistors Q31
~Q34 operates as a differential amplifier circuit, so the second
The input terminal 31 is connected to the collector of the transistor Q32.
, 32 is amplified and output. This amplified output is then transferred to a transistor Q35 which operates with the high impedance of the constant current source 34 as a load.
After being further amplified by , the output 15 is applied to the next stage circuit.

Assuming that the offset adjustment using the variable resistor VR31 has now been completed, the value e indicating the temperature characteristic proportional to the absolute temperature is e ≈ 3400 ppm, and the temperature characteristic f is the value e indicating the temperature characteristic proportional to the absolute temperature. Since a resistor is used, f=-300 ppm. Further, the temperature characteristic d of the constant current source 33 is d≒ e /
Since it is set to be f, d≈1+0.0037, and its temperature characteristic a is 3700 ppm.

Also, the temperature characteristics of the voltage between the terminal T11 and the terminal T12 of the variable resistor VR31, and the temperature characteristic of the voltage between the terminal T1
As already explained, the temperature characteristics of the voltage between T2 and terminal T13 are both proportional to the absolute temperature, e.
Therefore, the temperature characteristics of the voltage between the base of the third transistor Q33 and the ground level, and the temperature characteristics of the voltage between the base of the fourth transistor Q34 and the ground level are both proportional to the absolute temperature. Therefore, from the first transistor Q31 to the third transistor Q3
Temperature characteristics of the current when looking at the collector of 3 and the temperature characteristics of the current from the second transistor Q22 to the fourth transistor Q34
The temperature characteristics of the current when looking at the collector of is regardless of the position of the sliding terminal T32 of the variable resistor VR31.
370, both of which have a value equal to the temperature characteristics of the current of the constant current source 11.
It becomes 0ppm.

FIG. 4 is a circuit diagram showing the electrical configuration of a second embodiment of the invention.

Since this embodiment is substantially the same in configuration as the embodiment shown in FIG. 1, only the different parts will be explained, and the same parts will be designated by the same reference numerals as in FIG. will be given the reference numeral , and the explanation of its configuration will be omitted.

One terminal of a variable resistor VR32 is connected to the emitter of the third transistor Q33a, and the emitter of the fourth transistor Q34 is directly grounded. Further, the emitter area of the third transistor Q33a is twice the emitter area of the fourth transistor Q34. The other parts have the same configuration, and the temperature characteristics of the constant current source 33 are 3700p.
pm, and the temperature characteristic of variable resistor VR32 is -30
It is 0ppm. In this embodiment as well, the variable resistor VR32 is connected to the emitter of the third transistor Q33a because the temperature characteristic of the voltage between the terminals of the variable resistor VR32 is approximately 3400 ppm, which is proportional to the absolute temperature. The collector current of the third transistor Q33a and the fourth transistor Q33a can be ignored.
The temperature characteristics of the collector current of transistor Q34 are as follows:
Both have the same amount of 3700 ppm.

It should be noted that the present invention is not limited to the above embodiments, and for all transistors, PNP transistors are
The present invention can be similarly applied to a configuration in which a PN transistor is used and the NPN transistor is replaced with a PNP transistor.

[0036] Also, variable resistors VR11, VR12, VR
31. Regarding VR32, its temperature characteristics are -300p
Although the case of pm has been described, the present invention can be similarly applied to cases of other temperature characteristics.

[0037]

Effects of the Invention In the integrated differential signal circuit according to the present invention, the value of the temperature characteristic of the variable resistor for offset adjustment connected to the emitter of the transistor constituting the current mirror circuit is C, and the current Let A be the temperature characteristic of the constant current source that determines the current value of the mirror circuit, and B be the temperature characteristic proportional to the absolute temperature. Since the value A is set in the relationship A≒B/C, offset adjustment is necessary. Since the temperature characteristics are the same as when ignoring the fact that the variable resistor is connected to the emitter, it is possible to prevent offset deviation due to changes in environmental temperature.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the electrical configuration of a first embodiment of the invention as set forth in claim 1. FIG.

FIG. 2 is a circuit diagram showing the electrical configuration of a second embodiment of the invention as claimed in claim 1.

FIG. 3 is a circuit diagram showing an electrical configuration of a first embodiment of the invention as claimed in claim 2;

FIG. 4 is a circuit diagram showing the electrical configuration of a second embodiment of the invention as claimed in claim 2;

FIG. 5 is a circuit diagram showing an electrical configuration of a conventional technique.

[Explanation of symbols]

11 Constant current source 12 Current mirror circuit 33 Constant current source G11 Second power supply terminal P11 First power supply terminal Q11 First driven transistor Q12 Second driven transistor Q15 Drive transistor Q21 First transistor Q22 Second transistor Q31 First transistor Q32 Second transistor Q33 Third transistor Q34 Fourth transistor VR11 Variable resistor VR31 variable resistor

Claims (2)

[Claims] Claim 1: When one of a pair of power supply terminals is set as a first power supply terminal and the other is set as a second power supply terminal, and a transistor to which a current is input in a current mirror circuit is set as a drive transistor, the drive transistor is a constant current source whose output is connected to the collector; and a pair of transistors provided corresponding to the pair of outputs of the current mirror circuit, the base of which is connected to the base of the drive transistor, A pair of driven transistors whose emitters are supplied with current from one power supply terminal, one of the pair of driven transistors is the first driven transistor, and the other is the second driven transistor, the first driven transistor has its emitter connected to the collector of the first transistor, has its collector connected to the second power supply terminal, has its emitter connected to the collector of the first transistor to which the input signal is guided, and the second driven transistor; a second transistor having a second power supply terminal connected to its collector and having an input signal conducted to its base; and a second transistor having a second power supply terminal connected to the emitter of at least one of the first and second driven transistors. The temperature characteristic of a variable resistor that is connected and is an external element that changes the ratio of the collector current of the first driven transistor and the collector current of the second driven transistor is c, and the temperature characteristic of the constant current source is a, When the temperature characteristic proportional to absolute temperature is b, the temperature characteristic a of the constant current source is a
A differential signal circuit formed into an integrated circuit, characterized in that the value is approximately b/c. 2. A pair of transistors each having an emitter connected to a constant current source and an input signal being introduced to each base; one of the pair of transistors being connected to a first transistor;
and the other is a second transistor, a third transistor whose collector and base are connected to the collector of the first transistor, a third transistor whose collector is connected to the collector of the second transistor, and a third transistor whose collector and base are connected to the collector of the first transistor. 3
A fourth transistor whose base is connected to the base of the transistor
an external element, the terminal of which is connected to the emitter of at least one of the third and fourth transistors, and which changes the ratio between the collector current of the third transistor and the collector current of the fourth transistor. When the temperature characteristic of the variable resistor is f, the temperature characteristic of the constant current source is d, and the temperature characteristic proportional to absolute temperature is e, the temperature characteristic d of the constant current source is d≒e.
An integrated differential signal circuit characterized by having a value of /f.