JP2004072681A - Comparator circuit and semiconductor integrated circuit having same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a comparator circuit in which a reference voltage circuit is not required, a semiconductor circuit comprises offset, temperature characteristics that the offset voltage substantially has are compensated, and a threshold level to switch the output of a comparator can be also adjusted. <P>SOLUTION: In the comparator circuit wherein a pair of transistors 2 and 3 are made asymmetric by changing a dimension ratio therebetween, a differential amplifier circuit increasing generation of an offset voltage Eoff in advance is provided, and an output is inverted in the state that the potential difference of differential inputs is comparatively large, one differential input is connected to a predetermined potential, e.g., a ground level GND and the comparator circuit has a means for setting a threshold Eth of a comparator input signal Ein to be connected between the potential GND and the other differential input In to a predetermined value. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a comparator circuit, and more particularly to a comparator circuit that does not require a reference voltage circuit for forming a threshold of a comparator input signal, and a semiconductor integrated circuit having the circuit.
[0002]
[Prior art]
FIG. 3 shows a comparator circuit according to the prior art. In FIG. 2, the comparator circuit has gate electrodes of P-channel MOSFETs (hereinafter abbreviated as Pch-MOSFETs) 12 and 13 as differential inputs, and connects to the current source 11 with the source electrodes of the Pch-MOSFETs 12 and 13 common. I do. The drain electrodes of the Pch-MOSFETs 12 and 13 are connected to the drain electrodes of N-channel MOSFETs (hereinafter abbreviated as Nch-MOSFETs) 14 and 15, and the gate electrode and the drain electrode of the Nch-MOSFET 14 are short-circuited. , 15 are commonly connected, and the source electrode is commonly grounded to ground (ground level GND) to form a current mirror circuit. The drain electrode of the Nch-MOSFET 15 is connected to the gate electrode of the Nch-MOSFET 18. The source electrode of the Nch-MOSFET 18 is grounded, the constant current source 17 is connected to the drain electrode, and the drain is configured as a comparator output OUT.
[0003]
The setting of the threshold value of the comparator circuit can be performed by applying the reference voltage Vref generated by the reference voltage circuit 16 to the gate electrode of the Pch-MOSFET 12 constituting the differential amplifier circuit.
In the comparator circuit of the prior art, the dimensions of the Pch-MOSFETs 12 and 13 forming the differential amplifier circuit are equal, and the dimensions of the Nch-MOSFETs 14 and 15 forming the current mirror circuit are also equal. The comparator output is inverted under the condition that the potentials of the differential input terminals of the differential amplifier circuit are equal, that is, the condition that the gate electrode of the Pch-MOSFET 13 is equal to the reference voltage Vref generated in the reference voltage circuit 17.
[0004]
Further, there are the following prior art documents. JP-A-2-117208 "Circuit device using complementary MOS technology", JP-A-4-185224 "Dropper type constant voltage circuit overcurrent protection circuit", JP-A-6-347493 "Circuit device for rectification of AC voltage signal", Kaihei 10-123182 "Window comparator circuit", JP-A-2001-211037 "Temperature detection circuit" and the like. Although individual illustration is omitted, the drawing number and the member number are quoted as they are in the literature, and simple comments are described below.
[0005]
Japanese Patent Application Laid-Open No. 2-117208 "Circuit device based on complementary MOS technology" discloses that, in FIG. 1, the transistors M1 and M2 constituting a differential amplifier circuit are made symmetrical and the transistors M3 and M4 constituting a current mirror circuit are made asymmetrical. Thus, the comparator operation is performed by forming a small offset voltage in the differential amplifier circuit.
JP-A-4-185224 "Overload protection circuit for dropper-type constant voltage circuit" is the same as JP-A-2-117208 described above if only the configuration of the comparator circuit is taken up. By making the transistors Q6 and Q7 constituting the circuit symmetrical and the transistors Q4 and Q5 constituting the current mirror circuit asymmetrical, the differential amplifier circuit forms a slight offset voltage ΔV to perform the comparator operation, The point potential is increased, the transistor Q11 is turned on, the main output transistor Q9 is turned off, and the dropper type constant voltage circuit has a current drooping characteristic at the time of overcurrent.
[0006]
Japanese Unexamined Patent Application Publication No. 6-347493 discloses a circuit device for rectifying an AC voltage signal by asymmetricalizing the transistors (T1, T2) and (T3, T4) of two sets of differential amplifier circuits. A rectifier circuit operation is obtained by obtaining the square characteristic. They are similar in that the transistors (T1, T2) of the differential amplifier circuit are asymmetric, but have different tasks and effects, and are not related to the present invention.
[0007]
Japanese Patent Application Laid-Open No. Hei 10-123182 discloses a "window comparator circuit" in which transistors (Q1, Q2) and (Q3, Q4) of two sets of differential amplifier circuits are asymmetric, and one output of the differential amplifier circuit is connected to the other. And the other output of the two sets of differential amplifier circuits is made asymmetric with the transistors Q9 and Q19 constituting the current mirror circuit, so that the input signal becomes equal to the reference voltage Vref. Is a window comparator circuit whose detection sensitivity is increased at a predetermined shift position. This prior art document has similar constitutional requirements that the differential amplifying circuit is asymmetric and the current mirror circuit is also asymmetrical. However, the reference voltage Vref of the present invention, which will be described later, is unnecessary, and an offset is formed by a semiconductor circuit. In this case, the offset voltage essentially has a temperature characteristic. However, the present invention provides a comparator circuit capable of compensating for the temperature characteristic and adjusting the threshold value at which the output of the comparator is switched. Has nothing to do with it.
[0008]
Japanese Patent Application Laid-Open No. 2001-211037 "Temperature detection circuit" discloses a temperature detection method using a semiconductor temperature sensor. Although not shown, in FIG. 1 of the document, the transistors 2 and 5 are configured as a source follower circuit, and connected to the drains of transistors 4 and 7 forming a current mirror circuit via resistors 3 and 6. The drain is connected to the output transistor 9 to form a temperature detection circuit.
[0009]
By selecting the resistors 3 and 6 to be equal and the characteristics (that is, dimensions) of the transistors 4 and 7 to be equal, the gate signal of the transistor 9 is input to the gates of the transistors 2 and 5 constituting the source follower circuit. A difference occurs between the signal difference and the forward voltage drop Vsd when the transistor 4 is driven with a predetermined current. Therefore, by setting the difference signal between the input signal difference input to the gates of the transistors 2 and 5 and the forward voltage drop Vsd of the transistor 4 to a predetermined value, a comparator operating at a predetermined temperature is configured. be able to.
[0010]
FIG. 3 of the document shows that a different operating current is applied to a plurality of serially connected diodes or transistor arrays 102 and 104 and the number of connected diodes or transistor arrays 102 and 104 is changed, so that the comparator 24 At the input, a comparator operating at a predetermined temperature can be configured.
As in the other documents described above, this disclosed document also eliminates the need for the reference voltage Vref, configures an offset with a semiconductor circuit, makes it possible to compensate for the temperature characteristic inherent in the offset voltage, and provides a comparator. The problem and the effect of providing a comparator circuit that can also adjust the threshold at which the output is switched are different, and are not related to the present invention.
[0011]
[Problems to be solved by the invention]
As described above, the conventional comparator circuit generally requires a reference voltage circuit to set an input threshold. For this reason, there is a problem that it is difficult to reduce the current consumption of the entire semiconductor integrated circuit because there are current consumption in the two circuit blocks of the comparator circuit itself and the reference voltage circuit.
[0012]
Further, some of the disclosed documents use a comparator circuit in a state where an offset is intentionally generated in a differential amplifier circuit, and do not require a special reference voltage circuit. However, they do not take into account the temperature characteristics inherent in the offset voltage, and are generally used where severe conditions are not required for the threshold to be compared, such as overcurrent protection.
[0013]
The present invention has been made in view of the above points, and has as its object to solve the above-described problems, eliminate the need for a reference voltage circuit, and configure an offset with a semiconductor circuit. It is an object of the present invention to provide a comparator circuit capable of compensating a temperature characteristic of the comparator and adjusting a threshold level at which the output of the comparator switches, and a semiconductor integrated circuit incorporating the comparator circuit.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a comparator circuit according to the present invention changes the dimensional ratio of a pair of transistors constituting a differential input so as to be asymmetric, or a current flowing to the drain or collector side of a transistor constituting a differential input. A mirror circuit is configured, the current mirror circuit is provided with a differential amplifying circuit having an asymmetrical structure by changing the dimensional ratio of the transistor and having an offset voltage at the differential input, and an output based on the potential difference of the offset voltage of the differential input. In the inverting comparator circuit, one differential input is connected to a bias power supply of the comparator circuit, and a source or an emitter of at least one of the transistors constituting the differential input of the differential amplifier circuit has a comparator input signal. It is assumed that a resistor for compensating the threshold temperature characteristic is connected.
[0015]
With this configuration, the comparator circuit sets the operating current ratio (for example, the source current or the emitter current) of the transistors constituting the differential input to a predetermined ratio, and sets the operating current and the temperature compensation inserted on the source or emitter side. The initial value of the threshold value of the comparator input signal can be adjusted by configuring the differential amplifier circuit asymmetrically due to the voltage drop with the resistor. The temperature characteristic due to the offset voltage generated as a result is corrected by the inserted resistor.
[0016]
Further, if a current mirror circuit is formed on the drain or collector side of the transistor constituting the differential input, and the current mirror circuit is made asymmetric by changing the dimensional ratio of the transistor, an offset voltage generated in the differential amplifier circuit is obtained. The amount can be increased, and the degree of freedom in designing the initial value of the threshold value of the comparator input signal can be increased.
[0017]
Further, the resistor connected to the source or the emitter side can have a positive temperature characteristic.
With such a configuration, the temperature characteristic of the offset voltage generated in the differential amplifier circuit generally has a negative temperature coefficient. Therefore, by setting the resistor inserted on the source or the emitter side to a positive temperature coefficient, the temperature of the input voltage as a comparator input signal can be increased. The potential input to the gate or base electrode can be made substantially constant.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a circuit diagram of a comparator circuit according to an embodiment of the present invention, and the same members corresponding to FIG. 3 are denoted by the same reference numerals.
In FIG. 1, a comparator circuit according to the present invention has a differential amplifier circuit in which the size ratio of two transistors 2 and 3 is changed to be asymmetric and the generation of an offset voltage Eoff is increased in advance. In a comparator circuit whose output is inverted in a relatively large state,
One differential input is connected to, for example, a ground level GND, and resistors 6 and 7 are provided to compensate for the temperature characteristics of the offset voltage.
[0019]
When the resistors 6 and 7 are provided, the threshold Eth of the comparator circuit input signal Ein also changes. Therefore, in order to set the threshold Eth to a predetermined value, it is necessary to consider the resistors 6 and 7 together.
With this configuration, the comparator input signal Ein connects the gate or base electrode of one of the differential input transistors 2 to, for example, the ground level GND, and sets the gate or base potential of the transistor 2 to a predetermined operating current value. From Vth2, the difference (Vth2−Eoff) between the offset voltages Eoff generated asymmetry by changing the transistor dimensional ratio of the differential input becomes the input signal Ein of this comparator circuit, and the input signal Ein at which the comparator output switches becomes the threshold Eth. . With this configuration, the comparator circuit can eliminate the need for the reference voltage circuit 16 in the related art.
[0020]
In particular, resistors 6 and 7 having temperature characteristics are connected to the sources or emitters of the transistors 2 and 3 constituting the differential input having a large offset voltage Eoff, respectively, and the resistance values are adjusted to obtain the comparator input signal Ein. The initial value and the temperature characteristic of the threshold value Eth can be adjusted.
Further, a current mirror circuit (4, 5) is formed on the drain or collector side of the transistors 2 and 3 constituting the differential input, and the dimensional ratio of the transistors 4 and 5 of the current mirror circuit (4 and 5) is changed. By adjusting the current ratio (for example, the operating current of the transistor 5 is twice that of the transistor 4), the initial value of the threshold value Eth of the comparator input signal Ein can be adjusted, and the degree of freedom in design can be increased.
[0021]
With such a configuration, the current ratio is adjusted to, for example, twice by changing the dimensional ratio of the transistors 4 and 5 of the current mirror circuit, so that the transistors 2 and 3 forming the differential input corresponding to the threshold value Eth of the comparator input signal Ein. The operating current ratio can be set to the dimensional ratio of the transistors of the current mirror circuit. From the operating current ratio, as described above, the operating current and the resistors 6 and 7 having temperature characteristics inserted on the source or emitter side can be used. , The influence of the temperature characteristics due to the offset voltage Eoff generated in the differential amplifier circuit can be corrected by the inserted resistor. In this configuration, the offset voltage amount Eoff generated in the differential amplifier circuit can be considerably changed by changing the dimensional ratio of the transistors of the current mirror circuit, and the initial value of the threshold value Eth of the comparator input signal Ein and its temperature characteristics Design flexibility can be increased.
[0022]
【Example】
The comparator circuit according to the present invention will be supplementarily described below with an example of a MOSFET transistor. In the comparator circuit according to one embodiment of the present invention, the dimensional ratio of the Pch-MOSFET transistors 2 and 3 constituting the differential input is selected to 1: 5, and the dimensions of the Nch-MOSFET transistors 4 and 5 constituting the current mirror circuit are determined. The ratio is selected to be 1: 2, the resistance 6 connected to the source electrodes of the Pch-MOSFET transistors 2 and 3 is 1 kΩ, the resistance 7 is 20 kΩ, and the gate electrode of the Pch-MOSFET transistor 2 is grounded to the ground GND. Other configurations are the same as those of the conventional circuit example. Regarding the dimensional ratio, for example, it is assumed that the characteristics of a transistor having a size of 5 are equivalent to those obtained by connecting five transistors having a size of 1 in parallel.
[0023]
The input offset voltage can be made relatively large by the dimensional ratio of the transistors (2, 3) and (4, 5), the resistance value of the resistors (6, 7) and the temperature characteristics of the resistors (6, 7). The input threshold value Eth can be set arbitrarily for the input signal Ein from the GND level, and the temperature coefficient of the input threshold value Eth can be adjusted to an appropriate value.
In one embodiment of the component constants described above, a temperature coefficient of almost zero could be obtained with a threshold of 0.3 V as the input threshold Eth.
[0024]
Although the above description has been made with reference to MOSFETs, it is also possible to use PNP and NPN bipolar transistors. In the case of a bipolar transistor, it is preferable to float, for example, the potential of one diode, rather than connecting the base electrode of the transistor 2 directly to the ground GND. This is because the base-emitter forward voltage of the transistor 2 is about 0.7 V, and the transistor including the current mirror circuit falls within this voltage range because the transistor easily enters the saturation region. This is to provide a margin of potential for one minute.
[0025]
As described above, to summarize the present invention,
(1) The dimensions of the transistors 2 and 3 constituting the differential input are made asymmetrical,
(2) Insert the resistors 6 and 7 into the sources or emitters of the transistors 2 and 3 of this differential amplifier circuit,
(3) The dimensions of the transistors 4 and 5 constituting the current mirror circuit are made asymmetric.
[0026]
The occurrence of the offset Eoff of the differential amplifier circuit is intentionally increased by one or a combination of a plurality of these three items, and the initial value and the input threshold value of the input threshold value Eth are adjusted by adjusting the resistors 6 and 7 nodes. The temperature characteristics of Eth can be made substantially zero.
As a result, in the prior art, the differential amplifier circuit is generally configured symmetrically, is not affected by the temperature characteristics, and requires a reference voltage circuit that can separately set the input threshold Eth. Without providing a new reference voltage circuit, the connection of the input terminal on one of the reference voltage circuits is connected to a fixed potential, for example, a ground GND level for a MOSFET, an external positive power supply serving as a bias power supply for a comparator circuit, or an external power supply. To the negative power supply. According to this method, an arbitrary input threshold value Eth can be set, and no special circuit is required for setting the input threshold value at which the output of the comparator is inverted. A semiconductor integrated circuit using the circuit can be provided.
[0027]
In the embodiment shown here, the Pch-MOSFET is used for the differential input and the Nch-MOSFET is used for the current mirror circuit. However, the circuit using the Nch-MOSFET for the differential input and the Pch-MOSFET for the current mirror circuit and the MOSFET are used for the bipolar. It is also effective in a circuit replaced with a transistor.
FIG. 2 shows another embodiment of the present invention in which an Nch-MOSFET is used as a differential input. A comparator circuit according to another embodiment of the present invention includes Nch-MOSFET transistors 22 and 23 forming a differential input, Pch-MOSFET transistors 24 and 25 forming a current mirror circuit, and source electrodes of Nch-MOSFET transistors 22 and 23. It has resistors 26 and 27 to be connected, and connects the gate electrode of the Nch-MOSFET transistor 22 to Vp.
[0028]
【The invention's effect】
As described above, according to the present invention, an input threshold can be set without a dedicated reference voltage circuit or without a reference voltage circuit itself, and the temperature characteristics of the input threshold can be compensated, A comparator circuit having a simple circuit configuration can be realized, and power consumption can be reduced at the same time. Further, when this comparator circuit is applied to a semiconductor integrated circuit, the circuit area of the comparator circuit is simple, so that the chip area can be made smaller and the cost can be reduced as compared with the related art.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a comparator circuit according to one embodiment of the present invention. FIG. 2 is a circuit diagram of a comparator circuit according to another embodiment of the present invention. FIG. 3 is a circuit diagram of a comparator circuit according to the prior art.
2, 3, 12, 13 PchMOS transistors 4, 5, 14, 15, 8 NchMOS transistors 6, 7 Resistors 11, 17 Constant current source 16 Reference voltage circuit Vp Power supply voltage GND Ground

Claims (4)

A comparator comprising a differential amplifying circuit having an asymmetrical structure by changing a dimensional ratio of a pair of transistors constituting a differential input and having an offset voltage at the differential input, and inverting an output based on a potential difference of the offset voltage of the differential input. In the circuit, one differential input is connected to a bias power supply of the comparator circuit, and a threshold temperature of a comparator input signal is connected to a source or an emitter of at least one of transistors constituting the differential input of the differential amplifier circuit. A comparator circuit to which a resistor for compensating characteristics is connected. The comparator circuit according to claim 1,
A comparator circuit, wherein a current mirror circuit is formed on the drain or collector side of the transistor forming the differential input, and a dimensional ratio of a pair of transistors forming the current mirror circuit is changed to be asymmetric. A pair of transistors constituting a differential input, a current mirror circuit constituting a drain or a collector side of the transistor constituting the differential input, and a differential amplifier circuit having an offset voltage at the differential input; At least one of the pair of transistors constituting the input and the pair of transistors constituting the current mirror circuit is made asymmetric by changing the dimensional ratio of the transistors, and the comparator inverts the output based on the potential difference of the offset voltage of the differential input. In the circuit, one differential input is connected to a bias power supply of the comparator circuit, and a threshold temperature of a comparator input signal is connected to a source or an emitter of at least one of transistors constituting the differential input of the differential amplifier circuit. Comparator characterized by connecting a resistor for compensating characteristics Over-capacitor circuit. 4. The comparator circuit according to claim 1, wherein:
The comparator circuit, wherein the resistor has a positive temperature characteristic.

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