JP2569944B2 - Current mirror circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current mirror circuit used, for example, in a subscriber circuit of an electronic exchange, and more particularly to a current mirror circuit whose operation time is improved.

[Conventional technology]

For example, in an electronic exchange, a current mirror circuit is used for a subscriber circuit.

FIG. 2 shows such a conventional current mirror circuit. Power V _CC input side transistor current mirror via a resistor R ₁ Q ₁ in the current mirror circuit
Connected to the emitter. The power supply V _CC is a resistor
_{R 21, R 22, ...... R} 23 a current mirror output transistors Q ₂₁ through respectively, Q _22, and is connected to the emitter of ...... Q _2N. Here, the numerical value N is a positive integer representing the number of outputs of the current mirror circuit. Current mirror output transistors Q _21, Q _22, based ...... Q _2N are connected to each other. In addition of these transistors Q _21, Q _22, ...
… The collectors of Q _2N are the output terminals T ₀₁ and T for the current mirror.
₀₂ , ...... Connected to _T0N . The collector of the input-side transistor Q ₁ for the current mirror is connected to the output terminal T _1.

In the current mirror circuit, when representing the current through the collector of the input side transistor Q ₁ for current mirror current I _IN1, the output current of the desired current mirror ratio I _OUT1, I
_OUT2, ...... I _OUTN each of the current mirror output transistors Q _21, Q _22, will be obtained from the collector of ...... Q _2N.

In this circuit it has been devised to reduce the error in the current mirror ratio due to the base current of the current mirror input side transistor Q ₁ and the output-side transistors _{Q 21, Q 22, ...... Q} 2N. That is, each connected transistors _{Q 1, Q 21, Q 22} , the emitter side of the ...... Q current gain compensation transistor Q ₀ to the base of _2N. Assuming that the current amplification factor of the current amplification factor compensating transistor Q ₀ is β ₀ , these transistors Q ₁ , Q ₂₁ ,
The base current of Q ₂₂ ,..., Q _2N is set to 1 / β ₀ .

Power V _CC and the collector of the current mirror input transistor Q _1, AC blocking capacitor C 'is connected. AC blocking capacitor C 'is input current I _IN AC components are removed from the current of the current flowing in the collector of the input side transistor Q ₁ current mirror only a DC component I _IN1
And

Transistor Q ₃ are connected to the emitter to a power source V _CC, and a collector connected to the collector of the input-side transistor Q ₁ current mirror. The base is connected to the output current control input terminal T ₃ of the current mirror circuit.
When the collector current of the collector output current controlling transistor Q ₃ is flow the base current that is larger than the input current I _IN, the transistor Q ₃ are saturated, the current mirror circuit is stopped. The collector current of the transistor Q ₃ by setting to zero the base current of the collector output current control transistor Q ₃ are next to zero, the current mirror circuit operates.

[Problem to be solved by the invention]

With such a conventional current mirror circuit, the output current I
_{When OUT1} , _IOUT2 ,..., _IOUTN are stopped, no charge is charged in the AC blocking capacitor C '. Therefore, when the output currents I _OUT1 , I _OUT2 ,..., I _OUTN shift from the stop state to the operation state, the rise time until the transistors Q ₀ and Q ₁ reach the operation voltage (base-emitter voltage). And the operating time becomes longer.

In order to shorten the operation time, the capacity of the AC interrupting capacitor C 'may be reduced. However, if the capacitance is reduced, the required AC cutoff frequency cannot be satisfied.

As described above, the conventional current mirror circuit has a problem that it is not possible to satisfy both of the two requirements such as the operation time and the AC cutoff frequency.

Accordingly, an object of the present invention is to provide a current mirror circuit that can satisfy these two requirements.

[Means for solving the problem]

According to the first aspect of the present invention, an input-side PNP transistor whose emitter is connected to a power supply via a resistor, and N transistors whose emitters are connected to a power supply via a resistor and whose base is commonly connected to the base of the input-side PNP transistor An output transistor, an AC blocking capacitor connected between the collector of the input PNP transistor and the power supply, an emitter connected to the base of the input PNP transistor and the output transistor, and a collector connected to the reference potential. The current amplification factor compensation PNP transistor whose base is connected to the collector of the input side PNP transistor via a resistor and the base is input, the emitter is connected to the power supply, and the collector is connected to the base of the current amplification factor compensation transistor. A current mirror circuit is provided with the connected collector output current control PNP transistor.

According to the second aspect of the present invention, the input-side NPN transistor whose emitter is connected to the power supply via the resistor, and the emitter is connected to the power supply via the resistor and the base is commonly connected to the base of the input-side NPN transistor. N output-side transistors, an AC-blocking capacitor connected between the collector of the input-side NPN transistor and the power supply, and an emitter connected to the base of the input-side NPN transistor and the output-side transistor. A current amplification factor compensation NPN transistor having a base connected to the collector of the input side NPN transistor via a resistor, a base connected to the input, an emitter connected to the power supply, and a collector used for the current amplification factor compensation. A current mirror circuit with a collector output current control NPN transistor connected to the base of the transistor To.

Further, in the invention according to claim 3, the reference potential according to claim 1 or 2 is set to the ground potential.

That is, according to the first or second aspect of the present invention, a resistor is connected between the collector of the input-side PNP transistor and the base of the current amplification factor compensating transistor, and the AC is cut off at a voltage of the product of the resistor and the input current. The operation time is shortened by charging the capacitor for use. In addition, the charging voltage of the AC interrupting capacitor when the output current is stopped is determined by the resistance _R0 and is independent of the capacitance of the capacitor, so that it is possible to simultaneously satisfy both the above-described conditions of the operation time and the AC interrupting frequency. Become.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to examples.

FIG. 1 shows a circuit configuration of a current mirror circuit according to an embodiment of the present invention. In this circuit, PN
Input for P-type current mirror transistors Q ₁ and current mirror output transistors _{Q 21, Q 22, ...... Q} 2N
Are connected to each other, and their emitters are connected to a power supply V _CC via resistors R ₁ , R ₂₁ , R ₂₂ ,..., R _2N , respectively. The collectors of the transistors Q ₂₁ , Q ₂₂ ,..., Q _2N are connected to current mirror output terminals T ₀₁ , T _{02 ,.} Input transistor Q ₁ for current mirror
The collector is connected to the output terminal T _1.

AC blocking capacitor C is connected between the collectors of the power supply V _CC and a current mirror input side transistor Q _1. The AC blocking capacitor C removes an AC component from the input current I _IN , and the current flowing through the collector of the input terminal Q ₁ for the current mirror is set as I _N1 only for the DC component.

The PNP current gain compensation transistor Q ₀ has its base connected directly to the collector of the input side transistor Q ₁ current mirror, the emitter input side transistor current mirror Q ₁ and the output-side transistors Q _21, Q ₂₂ …
... they are commonly connected to the base of Q _2N, and the collector is connected to the earthed as a reference potential.

Transistor Q ₃ of the PNP type, the output-side transistor current mirror _{Q 21, Q 22, ...... Q} 2N collector output current I
_OUT1 , _IOUT2 ,... _Are elements for controlling the operation and stop of _IOUTN . The emitter of the collector output current controlling transistor Q ₃ are connected to the power supply V _CC, and the collector is connected between one end of the base and the resistor R ₀ in the current gain compensation transistor Q _0. Base is connected to the output current control input terminal T ₃ of the current mirror circuit. The other end of the resistor R ₀ is connected to the connection point of the capacitor C AC blocking the collector of input-side transistor Q ₁ current mirror.

The current mirror circuit having the above configuration, current mirror output transistors _{Q 21, Q 22, ...... Q} 2N respective collector currents I _OUT1, I _OUT2, when ...... I _OUTN is stopped, the input current I _IN And the resistance R ₀ , the AC interrupting capacitor C is charged. Therefore, when moving to the operating state from a state where the output current is stopped, the current amplification factor compensation transistor Q ₀ and the input-side transistor Q ₁ for the current mirror operates in a short time by the charge voltage of the AC blocking capacitor C . Thereby, the operation time is reduced.

Further, in this current mirror circuit, the charging voltage of the AC interrupting capacitor C when the output current is stopped can be determined by the resistor _R0 . That is, since the charging voltage can be set independently of the capacity of the AC cut-off capacitor C for which the AC cut-off frequency is set, it is possible to simultaneously satisfy the requirements of both the operation time and the AC cut-off frequency. become.

In the embodiment, the current amplification factor compensating transistor Q ₀ ,
An input-side transistor Q ₁ and the collector output current control transistor Q ₃ current mirror is constituted by a PNP transistor, but it may be constituted by NPN transistors, of course.

〔The invention's effect〕

As described above, according to the present invention, even when the collector output current of the current mirror output-side transistor is stopped, the charge is charged to the AC cutoff capacitor. This has the effect of shortening the response time until

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a current mirror circuit according to one embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventionally used current mirror circuit. Q ₀ ...... current gain compensation transistor, Q ₁ ...... input-side transistor current _{mirror, Q 21, Q 22, ~Q} 2N ...... output-side transistor current mirror, Q ₃ ...... collector output current control transistor , C: AC blocking capacitor.

Claims (3)

(57) [Claims] An input-side PNP transistor having an emitter connected to a power supply via a resistor, and N common-connected bases of the bases of the input-side PNP transistor having an emitter connected to the power supply via a resistor. An output-side transistor, a capacitor for AC cutoff connected between the collector of the input-side PNP transistor and the power supply, an emitter connected to the base of the input-side PNP transistor and the base of the output-side transistor, and a collector connected to a reference potential. A PNP transistor having a base connected to the collector of the input-side PNP transistor via a resistor; a PNP transistor having a base as an input, an emitter connected to the power supply, and a collector connected to the power supply. A collector output current control PNP transistor connected to the base of the transistor. Current mirror circuit. 2. An input NPN transistor having an emitter connected to a power supply via a resistor, and N NPN transistors having an emitter connected to the power supply via a resistor and having a base commonly connected to the base of the input NPN transistor. An output-side transistor, an AC cutoff capacitor connected between the collector of the input-side NPN transistor and the power supply, an emitter connected to the base of the input-side NPN transistor and the output-side transistor, and a collector connected to a reference potential. And a base connected to the collector of the input-side NPN transistor via a resistor, and a base connected to the input, an emitter connected to the power supply, and a collector connected to the power supply. A collector output current control NPN transistor connected to the base of the transistor. Current mirror circuit. 3. The current mirror circuit according to claim 1, wherein the reference potential is a ground potential.