JPH10117130A - Current comparison comparator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the current comparison comparator which is small in circuit scale, and further operated at a low voltage. SOLUTION: A 1st input stage IIL1 is made up of a PNP transistor (TR) Q1 and an NPN TR Q2, and a difference current between an input current Iin and a constant current Iinj1 from a 1st constant current source IinjA is used to make the NPN TR Q2 conductive/nonconductive. Furthermore, a 2nd input stage IIL2 is made up of a PNP TR Q3 and an NPN TR Q4, and a difference current between a current from the 1st input stage IIL1 and a constant current Iinj2 from a 2nd constant current source IinjB is used to make the NPN TR Q4 conductive/nonconductive, and their outputs are given to a medium stage MC and an output stage OC consisting of a common emitter TR circuit, and output currents from output terminals Iout1, Iout2 are controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current comparison type comparator, and more particularly to a current comparison type comparator capable of reducing the number of components and lowering a driving power supply voltage.

[0002]

2. Description of the Related Art Generally, a current comparison type comparator is shown in FIG.
As shown in the figure, the input current I21 for the measurement purpose and the input current I22 as the reference current are input to the current-voltage conversion circuits 23 and 24, respectively, and the voltages V25 and V26 are respectively input.
Convert to The converted voltages V25 and V26 are input to a comparison circuit 27, and an output voltage V based on a difference between the two is output.
28. As the comparison circuit 27, various circuit configurations are used depending on the purpose of use and desired characteristics. Basically, a constant current source, a differential amplifier, a current mirror circuit, and an output stage (such as an emitter follower and a push-pull circuit) are used. It is composed of Then, a drive power supply voltage range for stably operating the circuit is set by the configuration means, the number of used Trs, and the like.

FIG. 5 is a circuit diagram showing one example of such a circuit. In particular, FIG. 5 is a circuit diagram showing an example of circuits 23 and 24 for converting an input current into a current. This circuit is described in Japanese Patent Application No. 3-25899 and the drawing, and includes a resistor R31 having one end connected to the higher power supply line 31, a resistor R31,
Of the input current I
constant current source I for flowing a current Ii proportional to in (not shown)
31 and a resistor R32 having one end connected to the higher power supply line 31.
And a constant current source I32 connected between the other end of the resistor R32 and the lower power supply line 32 and flowing the reference current I _REF . Then, the comparing section 33 compares the potential V31 at the connection point between the resistor R31 and the constant current source I31 and the potential V32 at the connection point between the resistor R32 and the constant current source I32, and determines the magnitude relation between the comparison result and the output terminal V33. Is output.

FIG. 6 shows another example.
A current-voltage conversion circuit corresponding to 24 includes an operational amplifier, and an input current I4 is connected by a resistor R41 connected between an inverting input terminal 42 and an output terminal 44 of the operational amplifier 41.
1 is converted into a voltage, a DC voltage V41 is applied to the ratio inverting input terminal 43 of the operational amplifier 41, and a voltage at the output terminal 44 is (V41−I × R). Therefore, a current comparison type comparator can be configured by arranging two circuits in parallel and connecting a comparison unit to each output.

[0005]

However, such a conventional current comparison type comparator has the following problems. The first problem is that the number of components of the circuit increases. Because the number of parts increases,
The chip occupies a large area. The reason is that the conventional current comparison type comparator uses a current-voltage conversion circuit to compare the two input currents of the measured current and the reference current, and converts the input current to a voltage. Since the comparison is performed, the configurations of the current-voltage conversion circuit and the comparison circuit unit are complicated. For example, in the case of the circuit of FIG. 5, an operational amplifier is required to configure the comparison unit 33, and a large number of transistors are required to configure the operational amplifier. In the case of the circuit of FIG. 6, an operational amplifier is necessary for the current-voltage conversion circuit,
Similarly, the configuration is complicated.

[0006] The second problem is that the driving power supply for operating the circuit stably increases. The reason is,
Although depending on the circuit configuration of the output stage of the comparison circuit section, generally, the power supply at which the circuit operates stably is determined by the base-emitter voltage V _BE of the transistor in the output stage. Therefore, when the current-voltage conversion circuit and the comparison circuit unit are complicated for the purpose of improving and improving the electrical characteristics, the number of transistors increases, and the power supply voltage for operating the circuit stably increases. At present, as a general comparison circuit, a low power consumption type power supply voltage of up to about 3 V has been developed.

An object of the present invention is to provide a current comparison type comparator having a small circuit size and operating at a low voltage.

[0008]

A current comparison type comparator according to the present invention comprises a logic circuit composed of a transistor which compares an input current with a constant current from a constant current source and outputs an output according to the comparison result. It is characterized by comprising an input stage and an output stage comprising a voltage-driven transistor circuit for controlling a current to an output terminal based on an output of the input stage. In particular, the input stage has a configuration in which at least a constant current and an input current are input to a base, and a transistor is turned on and off according to a difference current between the constant current and the input current. The input stage includes a first input stage and a second input stage connected in series.
The input stage has a first transistor to which an input current and a first constant current are supplied to a base, and the second input stage has a collector current and a second constant current of the first transistor. A second transistor supplied to the base is provided, and a collector current of the second transistor is used as an output current.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a circuit configuration of a first embodiment of a current comparison type comparator according to the present invention.
In this figure, this circuit has a first equivalent of a NAND gate.
And second input stages IIL1 and IIL2, an intermediate stage MC that performs a comparison operation based on the output of the second input stage IIL2, and an output stage OC. The first input stage IIL1 includes a PNP transistor Q1 and an NPN transistor Q2, and has a measurement current input terminal Ii.
n1 is connected to the collector of the PNP transistor Q1 and the base of the NPN transistor Q2. The base of the PNP transistor Q1 is grounded to GND, the emitter is connected to a constant current source IinjA for supplying an injector current, and the constant current Iinj1 is supplied. The emitter of the NPN transistor Q2 is grounded to GND, and the collector is connected to the second input stage IIL2.

The second input stage IIL2 has a PNP transistor Q3 and an NPN transistor Q4,
The collector of the NPN transistor Q2 is connected to the collector of the PNP transistor Q3 and the base of the NPN transistor Q4. The base of the PNP transistor Q3 is grounded to GND, the emitter is connected to a constant current source IinjB for supplying an injector current, and the constant current Iin
j2 is supplied. The emitter of NPN transistor Q4 is grounded to GND, and the collector is connected to intermediate stage MC.

The middle stage MC includes PNP transistors Q5 and Q5.
The output stage OC includes NPN transistors Q7 and Q8. PNP transistor Q
The collector of the NPN transistor Q4 is connected to the base of the transistor 5. The collector of the NPN transistor Q2 is connected to the base of the PNP transistor Q6. The collector of the PNP transistor Q6 is GN
D is grounded, and the emitter is connected to the collector of PNP transistor Q5 and the base of NPN transistor Q8. The emitter of PNP transistor Q5 is connected to a constant current source and the base of NPN transistor Q7. N
The emitter of the PN transistor Q7 is grounded to GND, and the collector is connected to the constant current source and the output terminal Iout1. The emitter of the NPN transistor Q8 is GND
And the collector is connected to the constant current source and the output terminal Iout2.
It is connected to the. The other end of the constant current source is connected to a stabilized DC power supply.

Next, the circuit operation of the current comparison type comparator configured as described above will be described. First, the input stage II
In L1 and IIL2, when the input current Iin1 is smaller than the injector current Iinj1 (Iin1
In <Iinj1), a current substantially equal to Iinj1-Iin1 flows into the base of the NPN transistor Q2.
Also, Iinj is connected to the collector of PNP transistor Q3.
A current approximately equal to 2 flows. NPN transistor Q2
Since the current of Iinj1-Iin1 flows into the base of the NPN transistor Q2, the collector of the NPN transistor Q2 draws a current hFE2 (current amplification factor of the transistor Q2, the same applies hereinafter) times the base current. It turns on. Therefore, the injector current Iinj2 of the PNP transistor Q3 is completely
When pulled into the collector of N transistor Q2, N
No current is supplied to the base of the PN transistor Q4,
Q4 is turned off, and its collector terminal is equivalently opened.

As a result, the PNP transistor Q5 is turned off (does not operate), and the constant current I1 is supplied to the NPN transistor Q5.
7, the NPN transistor Q7 is turned on.
Then, the constant current I2 flows into the GND, and no current is output to the output terminal Iout1. On the other hand, since the NPN transistor Q2 is turned on (operates), the PNP transistor Q6 is turned on, the base voltage of the NPN transistor Q8 is applied only to the voltage between the emitter and the collector of the PNP transistor Q6, and the NPN transistor Q8 is turned off. The current I3 flows to the output terminal Iout2.

Next, when the input current Iin1 is larger than the injector current Iinj1 (Iin1-Ii
In nj1), the injector current Iinj1 is all pulled to the input terminal 1 side. As a result, the injector current Iinj1 does not flow into the base of the NPN transistor Q2, so that the NPN transistor Q2 is turned off. When the NPN transistor Q2 turns off, the collector terminal of the NPN transistor Q2 becomes equivalently open, and the injector current Ii of the PNP transistor Q3
nj2 flows into the base of NPN transistor Q4. For this reason, a current of Iinj2 × hFE4 times flows into the collector of the NPN transistor Q4, and the NPN transistor Q4 is turned on. Therefore, the voltage between the emitter and the collector of the NPN transistor Q4 becomes low, and the base voltage of the PNP transistor Q5 which is a common line also becomes low.

As a result, the voltage difference between the emitter and the base of the PNP transistor Q5 increases, and the PNP transistor Q5 turns on. At this time, by making the constant current I1 smaller than (injector current Iinj2 × hFE4 × hFE5), when the PNP transistor Q5 is turned on,
The constant current I1 all flows into the emitter of the PNP transistor Q5. Therefore, the constant current I1 is equal to the NPN transistor Q
No current flows into the base of the transistor 7, and the NPN transistor Q7 is turned off. As a result, the NPN transistor Q7
The constant current I2 connected to the collector of the output terminal Io
output to ut1.

Further, since the NPN transistor Q2 is off, the collector terminal of the NPN transistor Q2 is equivalently open and the common line PN
The base of the P transistor Q6 also becomes open (= han impedance). As a result, the PNP transistor Q6
Turns off, the constant current I1 flowing through the PNP transistor Q5 flows into the base of the NPN transistor Q8,
The PN transistor Q8 turns on. As a result, the constant current I3 flows from the emitter of the NPN transistor Q8 to the collector, that is, GND, and the output terminal Iout2
No current output.

As described above, according to this circuit configuration, the output state of the next and subsequent stages is changed depending on whether the injector current Iinj1 is larger or smaller than the input current Iin1, and the constant current I2 or I3 provided at the output terminal is changed. Can be output. Therefore, a current-voltage conversion circuit is not required, and an operational amplifier constituting a comparison unit having a large number of components is not required. Therefore, the number of transistors can be significantly reduced, the circuit configuration can be simplified, and the circuit scale can be reduced. In addition, the operating voltage can be reduced, and power consumption can be reduced.

However, in the embodiment of the present invention, the following conditions are required as is apparent from the above description. Iinj1 >> Iinj2 or Iinj1 × hFE2> Iinj2 Iinj2 × hFE4 × hFE5> I1 Base current driving capability of transistor Q7> I1 Base current driving capability of transistor Q8> I1 I1 × hFE7> I2 I1 × hFE8> I3

FIG. 2 is a circuit diagram of a second embodiment of the present invention. This circuit configuration includes first and second input stages IIL.
1, IIL2, an intermediate stage MC, and an output stage OC. The configuration of each of the input stages IIL1 and IIL2 and the configuration of the output stage are the same as in the first embodiment. The intermediate stage MC is different from the first embodiment in that the PNP transistor Q6 in the intermediate stage in the first embodiment is omitted and the number of components is reduced. That is, the PNP transistor Q6 is deleted, and instead, the NPN transistor Q6 is replaced.
8 is connected to the collector of NPN transistor Q2 and PN
That is, it is connected to the line to which the collector of the P transistor Q3 and the base of the NPN transistor Q4 are connected.

The operation of the second embodiment is the same as that of the first embodiment, and when the input current Iin1 is smaller than the injector current Iinj1 (Iin1 <Iin
In j1), the current of Iinj1-Iin1 flows into the base of the NPN transistor Q2. Further, a current substantially equal to Iinj2 flows through the collector of the PNP transistor Q3. Iin is connected to the base of NPN transistor Q2.
Since a current of j1-Iin1 flows, NPN
The collector of the transistor Q2 draws a current hFE times the base current. As a result, the voltage between the emitter and the collector of the NPN transistor Q2 becomes low potential, the base of the NPN transistor Q8 which is a common line also becomes low potential, and the NPN transistor Q8 is turned off. Therefore, constant current I3 is output from output terminal Iout2.
The operations of the intermediate stage and the output stage after the NPN transistor Q4 are the same as those in the first embodiment, and the constant current I2 is not output from the output terminal Iout1.

On the other hand, when the input current Iin1 is larger than the injector current Iinj1 (Iin1> Ii)
In nj1), all the injector current Iinj1 is pulled toward the input terminal Iin1. As a result, the injector current Iin is connected to the base of the NPN transistor Q2.
Since j1 stops flowing, the NPN transistor Q2
Turns off. When the NPN transistor Q2 turns off, N
The collector terminal of the PN transistor Q2 becomes equivalently open, the base of the NPN transistor Q8, which is a common line, becomes high potential, and the NPN transistor Q8 turns on. Thus, the constant current I3 connected to the collector of the NPN transistor Q8 is
To GND, and there is no current output at the output terminal Iout2. The operations of the intermediate stage and the output stage after the NPN transistor Q4 are the same as those in the first embodiment, and the constant current I2 is output from the output terminal Iout1.

FIG. 3 is a circuit diagram of a third embodiment of the present invention. Also in this embodiment, the configuration of the input stage is the same as that of each of the first and second embodiments, but here, the output stage OC is changed from the two-stage configuration of each embodiment to a single-stage configuration. . That is, the PNP transistor Q6, the NPN transistor Q7, and the NPN transistor Q8 corresponding to the intermediate stage and the output stage of the first embodiment are eliminated, so that the number of parts can be reduced and the drive can be performed at a lower voltage than in the previous embodiment. I have to. In this circuit, the drive power supply operates from about 1V.

In this configuration, when the input current Iin1 is smaller than the injector current Iinj1 (Iin
At 1 <Iinj1), a current substantially equal to Iinj1-Iin1 flows into the base of the NPN transistor Q2. Further, Ii is also connected to the collector of the PNP transistor Q3.
A current substantially equal to nj2 flows. Since a current of Iinj1-Iin1 flows into the base of the NPN transistor Q2, the collector of the NPN transistor Q2 draws a current hFE times the base current. PNP
When the injector current Iinj2 of the transistor Q3 is completely drawn into the collector of the NPN transistor Q2, no current is supplied to the base of the NPN transistor Q4, and the collector terminal is equivalently opened. As a result, the PNP transistor Q5 turns off, and the constant current I1 flows to the output terminal Iout1.

On the other hand, when the input current Iin1 is larger than the injector current Iinj1 (Iin1> Ii)
In nj1), all the injector current Iinj1 is pulled toward the input terminal Iin1. As a result, the base of the NPN transistor Q2 has the injector current Iin
Since j1 stops flowing, the NPN transistor Q2
Turns off. When the NPN transistor Q2 turns off, N
The collector terminal of the PN transistor Q2 becomes equivalently open, and the injector current Iinj2 of the PNP transistor Q3 flows into the base of the NPN transistor Q4. When the injector current Iinj2 flows into the base of the NPN transistor Q4, a current Iinj2 × hFE4 times flows into the collector of the NPN transistor Q4. Since the NPN transistor Q4 is turned on, the voltage between the emitter and the collector of the NPN transistor Q4 becomes low, and the base voltage of the PNP transistor Q5 which is a common line also becomes low. As a result, P
The voltage difference between the emitter and the base of the NP transistor Q5 increases, the PNP transistor Q5 turns on, and the constant current I1
Flows through the collector of the PNP transistor Q5 to GND, and no current is output to the output terminal Iout1.

As described above in each of the first to third embodiments, in each of the embodiments, when designing a circuit with the IIL configuration, the injector current indispensable for the IIL configuration is used as the threshold value of the comparison circuit. Since it is used, there is no need to add a current-voltage conversion circuit for converting a current value into a voltage value according to the prior art, which leads to a reduction in the number of components. Further, the input stage units IIL1 and IIL2 are of the current drive type and are not subject to the limitation of the power supply voltage. Strictly speaking, a voltage at which the transistors Q1 and Q3 are turned on, that is, a collector voltage of the transistors Q1 and Q2 is required to be about 0.8 V or more. In the first embodiment and the second embodiment, the transistor Q5 is a part of the transistor Q5 to Q8 constituting a stepped portion, and is driven when the emitter terminal voltage of the transistor Q5 is 2 V or more. 1 V in the second embodiment
If it is, drive it.

[0026]

As described above, according to the present invention, the input stage has a logic circuit configuration using transistors that are turned on and off in accordance with the current difference between the input current and the constant current. A circuit configuration that directly compares the input current eliminates the need for a current-to-voltage conversion circuit required in conventional circuits, reduces the number of components, enables chip integration, and reduces the circuit scale. Can be. In addition, since the input stage has a circuit configuration driven by current, there is no effect of being limited by voltage, so that low-voltage driving can be performed and power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a circuit diagram according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a third embodiment of the present invention.

FIG. 4 is a block diagram of a general current comparison type comparator.

FIG. 5 is a circuit diagram of an example of a conventional current comparison type comparator.

FIG. 6 is a circuit diagram of an example of a conventional current-voltage conversion circuit.

[Explanation of symbols]

 IIL1 First input stage IIL2 Second input stage MC Intermediate stage OC Output stage 1in1 Input current Iinj1 First constant current (first injector current) Iinj2 Second constant current (second injector current) I1, I2, I3 Constant current Iout1, Iout2 Output terminal Q1, Q3, Q5, Q6 NPN transistor Q2, Q4, Q7, Q8 PNP transistor

Claims (6)

[Claims] 1. An input stage comprising a logic circuit composed of a transistor for comparing an input current with a constant current from a constant current source and outputting an output according to the comparison result, and an output from the input stage. And an output stage comprising a voltage-driven transistor circuit for controlling the current to the output terminal. 2. The current comparison circuit according to claim 1, wherein the input stage includes a transistor to which at least a constant current and an input current are inputted to a base, and which is turned on and off in accordance with a difference current between the constant current and the input current. Type comparator. 3. An input stage comprising: a first PNP transistor having an emitter connected to a constant current source;
A first NPN transistor whose base is connected to a collector of the transistor and an input terminal to which an input current is input, wherein the base of the first PNP transistor and the emitter of the first NPN transistor are grounded; 3. The current comparison comparator according to claim 2, wherein the first NPN transistor is turned on and off in accordance with the magnitude of the input current flowing out and the magnitude of the output current of the constant current source to turn on and off the collector current. 4. An input stage comprising a first input stage and a second input stage connected in series, wherein an input current and a first constant current are based on the first input stage. And a second transistor provided to the second input stage portion, the collector current and the second constant current of which are supplied to the base of the second input stage. 2. The current comparison type comparator according to claim 1, wherein a collector current of the transistor is an output current. 5. The first input stage includes a first PNP transistor having an emitter connected to a first constant current source, a collector of the first PNP transistor, and an input terminal to which an input current is input. A first NPN transistor having a base connected thereto, wherein a base of the first PNP transistor and an emitter of the first NPN transistor are grounded, and a second input stage section includes a second constant current source. A second PNP transistor having an emitter connected to the second PNP transistor and the second PNP transistor
A second NPN transistor having a base connected to a line to which a collector current of the first NPN transistor is input;
The base of the PNP transistor and the emitter of the second NPN transistor are grounded, and the first NPN transistor and the second NPN transistor are connected in accordance with the magnitude of an input current flowing from the input terminal and an output current of the constant current source. 5. The current comparison type comparator according to claim 4, wherein the comparator is turned on and off to output a collector current on and off. 6. The current comparison comparator according to claim 1, wherein the output stage comprises a common emitter circuit capable of operating at a low voltage.