JPH0760352B2 - Temperature-compensated current source and voltage regulator using the same - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current supply circuit, and more particularly to a current supply circuit capable of generating a current having a regulated magnitude and a predetermined temperature characteristic. The present invention relates to an integrated circuit (IC) suitable for use in generating a voltage regulator voltage that can set a temperature coefficient.

BACKGROUND OF THE INVENTION There are many applications for circuits and systems that require a current source or source to generate a current having a predetermined temperature coefficient (TC) and a regulated magnitude that is independent of the supply voltage. More particularly, it may be desirable to utilize a current supply circuit that produces a current of magnitude having a positive TC that varies proportionally with absolute temperature. This current can cancel out the negative TC inherent in the PN junction of the transistor's differential pair, for example, keeping the gain of a differential amplifier with the transistor's differential pair substantially constant over temperature. Can occur as. Since an IC can generally be equipped with a large number of such differential amplifiers, it is possible to generate a plurality of such currents, each having a given magnitude and associated temperature coefficient, in a current supply circuit of the type described above. You may need what you can do. Applications for such temperature compensated current sources are associated with other circuits that produce a regulated output voltage with a known TC. This temperature-compensated current can be used to generate a voltage across a resistor with a positive TC, which in turn is placed in series with the negative TC base-emitter voltage of the NPN transistor. Generate a zero TC output voltage. These types of voltage regulators are sometimes referred to by those skilled in the art as bandgap voltage regulators.

Conventional voltage regulators typically include a pair of transistors operating at different current densities. The two transistors have a base-emitter voltage difference (Δ
V _BE ), interconnected with associated circuitry to generate a voltage proportional to V _BE ). This differential voltage is used to set the current in the emitter of one transistor and has a positive temperature coefficient (TC). The current in the emitter is used to generate a voltage that varies proportionally with absolute temperature, which in turn, in combination with the voltage on the negative TC, is substantially TC.
Produces a composite voltage of zero.

[Problems to be Solved by the Invention] Although such conventional regulators have considerable advantages, most, if not all, regulators are severely limited. For example, to prevent temperature compensating current errors caused by differences in collector-emitter voltages of two transistors, conventional regulators require complex feedback mechanisms to prevent mismatching of the two devices. . This mechanism is not desirable in integrated circuit designs because it requires excessive chip area. In addition, the voltage level and the temperature coefficient of the output regulation voltage of these conventional regulators cannot be set independently and are determined by the difference voltage ΔV _BE . Moreover, conventional regulators cannot generate an adjustable TC regulation voltage that is less than the value of the V _BE voltage of the transistor.

Therefore, there is a need for an improved integrated temperature compensated current source circuit that solves the problems of conventional temperature compensated current source circuits.

In addition, an output voltage that can be set to any voltage and temperature coefficient using a precision temperature-compensated current source without the aforementioned limitations of conventional regulators and without the need for complicated feedback circuits. There is a need for a regulator circuit to arise.

Therefore, it is an object of the present invention to provide an improved temperature compensated current source circuit.

Another object of the present invention is to provide a circuit that produces a current having a regulated magnitude and temperature coefficient and is suitable for fabrication in the form of an integrated circuit.

Yet another object of the present invention is to provide an improved voltage regulator.

Yet another object of the present invention is to provide an improved integrated voltage regulator circuit that produces an output voltage that can be set to a predetermined voltage level and temperature coefficient.

Yet another object of the present invention is to provide a voltage regulator with a temperature compensated current source that provides a current with an adjustable temperature coefficient.

[Means for Solving the Problems] According to the above and other objects, first and second transistors which operate at different current densities, and collectors thereof are provided.
An emitter-to-emitter conductive path is connected in series between the emitter of the second transistor and the circuit node, sinks current from the second transistor in response to the feedback current, and connects between the first and second transistors. A third transistor for generating a differential voltage having a positive TC, the differential voltage being used to set a collector current through the third transistor, and a base and an emitter of the third transistor. A temperature compensation current source having a circuit connected between and generating a current having a controllable magnitude and a negative TC at said circuit node, and connected to said circuit node and supplied to it at both ends. A voltage regulator with a resistive circuit that produces a voltage proportional to the sum of currents is provided.

EXAMPLES Referring now to the drawings, some examples of temperature compensated current sources of the present invention suitable for fabrication in integrated circuit form and used to set a regulated voltage. It is shown. It can be seen that corresponding components described in connection with the figures are designated with the same reference numbers. FIG. 1 shows the interconnection of the basic components and the reference cell 12 of the temperature-compensated current source 10.
The current source 10 has NPN transistors 14, 1 coupled to it.
Suitable for supplying fanout at terminal 20 to multiple current sources such as 6, and 18. The collectors of the current source transistors are connected to respective current utilization circuits 22, 24 and 26, each of which requires a current having a predetermined temperature characteristic which varies with absolute temperature.

The reference cell 12 of the temperature compensated current source 10 comprises a pair of NPN transistors 28 and 30 whose emitters are coupled to the base of NPN transistor 36 via resistors 32 and 34 respectively. The collector-emitter path of transistor 36 is coupled between the emitter of transistor 30 and a negative power supply conductor 38 which is supplied with a negative or ground reference voltage -V. Transistor 28 has a collector and a base that are transistor 30.
It is connected as a diode which is connected to the base of. A pair of current sources 40 and 42 are connected to currents I ₁ and
I ₂ is supplied to the collectors of transistors 28 and 30,
It is connected to a power supply conductor 44 which is supplied with a positive operating voltage V _CC . Feedback is based on a transistor 30
A buffered NPN transistor coupled to the collector of PT and its collector-emitter path connected between conductor 44 and output node 20 (to the base of transistor 36) and in series with resistor 48 to negative power supply conductor 38. By 46 to the base of transistor 36.

The concept of the present invention is to (1) generate a differential voltage having a positive temperature coefficient (TC), and (2) use this differential voltage to set the current flowing into the collector of transistor 36, Causing the magnitude to change with absolute temperature, (3) utilizing the negative TC base-emitter voltage drop V _BE of transistor 36 to generate a current with negative TC through resistor 56, and ( 4) consists of adding two currents at node 62 to produce a composite voltage whose value and temperature coefficient are controllable.

The differential voltage is generated in the present invention by operating transistors 28 and 30 at different current densities, which, as will be appreciated, produce a positive differential voltage ΔV _BE between the emitters of the two transistors. . In the present invention, transistor 28 has its emitter area N times larger than the emitter area of transistor 30 (where N is a positive number) and I _{1 is set} to I ₂
To operate at a lower current density than transistor 30. If resistor 32 is equal to resistor 34, the voltage appearing across the base-emitter of transistor 28 and across resistor 32 is equal to the voltage appearing across the base-emitter of transistor 30 and across resistor 34. However, since transistor 28 operates at a lower current density, its base-emitter voltage is less than the base-emitter voltage of transistor 30, and at rest the aforementioned equal voltages develop between their emitters. However, at first,
Transistor 28 sinks all of the current I ₁ and acts as a diode, thus biasing transistor 30 at that voltage. As the emitter of transistor 30 becomes (1 / N) times smaller than the emitter of transistor 28, transistor 30 initially sinks less collector current than the magnitude of I ₂ . This causes the collector voltage of the transistor 30 to rise, which causes the feedback transistor 46 to become conductive. Thus the transistor 46 supplies the base drive current to transistor 36, thereby the transistor 36 becomes conductive, the current flowing through the transistor 30 the current I _T from the emitter of the transistor 30 at its collector, I ₁
Sink until a current equal to I ₂ equals. By making the current through transistor 30 equal to the current through transistor 28, the feedback effect of the circuit produces a differential voltage ΔV _BE across its emitters. As a result, the voltage I _T absorbed by the transistor 36 is determined. Thus, I in a dormant operating state from the _{1 R32 + V BE28 = V BE30} + (I 2 -I T) The R34 and V _BE30 -V _BE28 = ΔV _BE, because it is _{I 1 R32 = I 2 R34,} I T = ΔV _BE / R34 where ΔV _BE = (KT / q) 1nN K = Boltzmann constant T = absolute temperature q = electron charge

Therefore, I _T is a temperature compensation current whose magnitude can be controllably set by the value of R34 and which varies directly with absolute temperature. NPN transistor 46 produces a feedback current that biases the base of transistor 36, ensuring that transistor 36 sinks the correct collector current. Transistor 46 also buffers the fanout base currents of current supply transistors 14, 16 and 18 so that they do not affect the operation of transistors 28 and 30. Resistor 48 is selected to sink a current greater than the sum of the currents flowing through resistors 32 and 34 to ensure a proper bias current for transistor 46. Transistor 36
By grounding its emitter and coupling the bases of current source transistors 14, 16, and 18 to terminal 20, all of the latter collector currents become temperature compensated currents as I _T changes. These currents can be scaled to any desired magnitude, for example by utilizing an emitter resistor or by setting the emitter area ratio. Therefore, transistor 16 has a resistor 49 in its emitter path, and transistor 18 is shown as having a plurality of emitters. Since the collector-base voltage of the transistors 28 and 30 is substantially equal to zero, the temperature-compensated current source cell 12 is relatively independent of fluctuations in the power supply voltage because the collector-emitter voltages of both transistors are well matched. is there.

Referring to FIG. 2, a pair of NPN transistors 50 and 5
2, which improve the accuracy of the temperature compensated current source 10. Transistor 50 has its collector-emitter path coupled between power supply conductor 44 and the bases of transistors 28 and 30 and its base connected to current source 40, but the base current to transistors 28 and 30 is To reduce the error between I ₁ and I ₂ . Similarly, transistor 52 has its collector-emitter path connected between power supply conductor 44 and the base of transistor 46, whose base is connected to current source 42 and buffers the base current of transistor 46.

FIG. 3 shows a temperature compensated current source 54 that produces an output current I _out with an adjustable temperature coefficient that utilizes the concepts disclosed above for the current source 10. Temperature compensated current source 54 comprises another resistor 56 coupled between the base and emitter of transistor 36 of reference cell 12. Therefore I _out is the base-emitter voltage of _{I out = I T + V BE36} / R56 and _{I out = ΔV BE / R34 +} V BE36 / R56 where V _BE36 is the transistor 36, R56 is the value of the resistor 56.

Since ΔV _BE has a positive TC and V _BE36 has a negative TC, the ratio of R34 to R56 is chosen to make TC of I _out positive, negative,
Or it can even be just zero. It is understood that the V _BE of transistor 36 is well controlled since its collector current is known to be ΔV _BE / R34.

By way of example, resistors 32 and 34 are shown above as being connected to the base of transistor 36. However,
It will be apparent from the present disclosure that resistors 32 and 34 can also be connected to any reference potential source at a common node so long as transistor 30 does not saturate. It will also be appreciated that transistor 52 can be utilized to buffer transistor 46 as shown in FIG.

FIG. 4 shows the voltage regulator 60 of the present invention including the temperature-compensated current source described above. In the preferred embodiment, output node 62 is connected in series with another resistor 64. Transistor 52 has its base-emitter path connected between the collector of transistor 30 and the base of transistor 46, with its collector coupled to conductor 44, with the collector of transistor 30 also connected to this at node 66. Buffering the effect of the load current supplied to the load means being provided. In addition, transistor 52 ensures that the collector voltage of transistor 30 is equal to the collector voltage of transistor 28 so that the two transistors do not become mismatched. The resistor 68 is connected between the emitter of the transistor 52 and the output terminal 66 and regulated at the output terminal 66 (regulate
d) Output voltage V _out is generated.

A voltage is developed across resistor 64 that is proportional to the current I _out and, in combination with V _{BE of} transistor 36, results in a composite voltage V _out . Therefore, V _out is as follows.

V _out = V _BE36 (1 + R64 / R56) + ΔV _BE R64 / R34 (4) where R64 is the value of the resistor 64.

Therefore, by properly selecting the ratio of resistors, V
_Out can be set to the desired voltage and temperature coefficient independently of each other.

Although V _out is taken at the output 66 in the preferred embodiment, it will be appreciated that the regulated output voltage will also occur at node 62 and can be used as the regulator output voltage.

While some embodiments of the invention have been described above in detail, it is understood that modifications may be made thereto, within the scope of the claims.

[Advantages of the Invention] As described above, according to the present invention, a temperature compensation current source for generating a temperature compensation current having an adjustable temperature coefficient;
Novel voltage regulation having means for generating a voltage proportional to the temperature-compensated current and combining this voltage with other voltages of different temperature coefficients to generate a composite voltage whose magnitude and temperature coefficient can be independently controlled. You get a bowl.

[Brief description of drawings]

FIG. 1 is a schematic electric circuit diagram showing a temperature compensation current source according to the present invention. FIG. 2 is a schematic electric circuit diagram showing a second temperature compensation current source according to the present invention. FIG. 3 is a schematic electric circuit diagram showing a third temperature compensation current source according to the present invention. FIG. 4 is a schematic electric circuit diagram showing a voltage regulator provided with the temperature-compensated current source of FIG. 10 ... Temperature compensation current source, 12 ... Reference cell, 14,16,18,28,30 ...
NPN transistor, 22, 24, 26 ... Current utilization circuit, 40, 42 ... Current source, 44 ... Conductor.

Claims (2)

[Claims] 1. A first and a second transistor having their bases coupled to each other and configured to conduct current through respective collector-emitter conductive paths, and said collector conductive path having said second transistor. A third transistor coupled to the emitter of the first transistor, a first resistor having one end substantially connected to the emitter of the first transistor and one end substantially coupled to the emitter of the second transistor A second resistor having the other end connected to the other end of the first resistor, the current flowing through the first transistor also flowing through the first resistor, and the second resistor Some of the current flowing through the transistor is also configured to flow through the second resistor; the collector of the second transistor and the base of the third transistor; Feedback circuit means coupled between and generating a bias current for conducting the third transistor to sink current from the second transistor, wherein the current flowing through the second transistor is the first A voltage difference that is proportional to the current through the transistors and has a predetermined temperature coefficient (TC) is generated between the emitters of these transistors, and the collector current of the third transistor is of a regulated magnitude and the A temperature-compensated current source, comprising: feedback circuit means having a predetermined temperature coefficient. 2. A first and a second transistor operating at different current densities and producing a differential voltage between them having a predetermined temperature coefficient, one end of which is connected substantially to the emitter of said first transistor. A first resistor and a second resistor having one end substantially connected to the emitter of the second transistor and the other end connected to the other end of the first resistor; A current flowing through the first transistor also flows through the first resistor, and a part of the current flowing through the second transistor is also configured to flow through the second resistor, A third transistor whose collector-emitter path is coupled between the emitter of the second transistor and a predetermined circuit node, and a base of the third transistor in response to the second transistor. Fee Providing a back signal, a third transistor having a predetermined magnitude from the emitter of the second transistor and having a predetermined magnitude such that the first and second transistors operate at the different current densities and the predetermined temperature. Feedback circuit means adapted to sink a current having a coefficient; temperature-compensated current source means; and a third node connected between the base and emitter of the third transistor. And a third resistor that supplies a current having a temperature coefficient that varies inversely to the temperature coefficient of the current flowing through the third transistor; and connected to the circuit node through the third resistor. The current flowing through the transistor and the third resistor is added to generate a regulated voltage across the transistor, independent of its magnitude and temperature coefficient. And a fourth resistor that can be set, and a voltage regulator.