JPS61228710A - Current source circuit - Google Patents

Abstract

PURPOSE:To obtain a current source circuit without flowing a waste current even at output open with simple circuit constitution by connecting respectively the 1st - 5th transistors (TR) by a specific method. CONSTITUTION:A TR 1 and an input current source 2 are connected in series between a power supply V<+>1 and common, bases of TRs 3, 5 are connected in common, an emitter of a TR 6 is led to an output current terminal 7 and a base of the TR 4 is connected to an input current source 2. In the circuit formed above, each base current of the TRs 1, 6 is equal by the mirror circuit comprising the TRs 3, 5. Thus, the output current is equal to the input current. When the output is opened, that is, the emitter of the TR 6 is opened, the base current of the TR 5 is very small while taking the emitter current of the TR 3 into account. Thus, the current increase through a power supply V<+>2 is negligible.

Description

[Detailed description of the invention] [Field of industrial use] 5 The present invention relates to a current source circuit suitable for integrated circuits.

[Conventional technology]

Various current source circuits have been proposed, and among them, a current mirror circuit as shown in FIG. 2 is conventionally known as a circuit in which the base current IB is compensated. Its configuration is such that a transistor 9 and an input signal source 8 are connected in series between a power supply v3 and the ground, while a transistor 11 is connected between an output terminal 12 and the ground, and a transistor 9 and a transistor 11 are connected in series between the output terminal 12 and the ground.
0 base and 1 are connected in common, and transistor 1 is connected there.
The emitter of ゜ is connected. The transistor 1o is used for TB compensation, and receives an input signal at its base, and its collector is connected to the power supply 4+.

[Problem that the invention seeks to solve]

However, in such a current source circuit, when the output is opened, the output transistor becomes saturated, and the base current increases significantly. Now, assuming that the forward current amplification factor of the transistor 11 is βF, the reverse direction 'It current amplification factor is βR1, and the input current is Iln, the base current when the collector of the transistor 1 is opened is - "〒F1X I I
n (here, βF is assumed to be flash).

βB is usually a low value of about 1 to 2. Now βR+=
If =1, the current will be 211 m, and this current will naturally be supplied from the power supply. Therefore, in a device with an open output state, lowering the current is significantly hindered.

[Means for solving problems]

According to the present invention, a first transistor whose emitter is led out to a current input terminal and whose collector is grounded, and a first transistor whose emitter is grounded and whose collector is connected to the base of the first transistor and which have different polarities. a third transistor having the same polarity as the second transistor and whose bases are connected to each other and whose emitters are grounded; and a third transistor whose base is connected to the current input terminal and whose bases are connected to each other and whose emitters are grounded. The third (D
a fourth transistor having the same polarity as the try') star;
A current source circuit comprising a fifth transistor having a polarity different from that of the third transistor, whose collector is grounded, whose base is connected to the collector of the third transistor, and whose emitter is led out to a current output terminal. can get.

〔Example〕

Next, the present invention will be explained in detail according to an embodiment thereof using the drawings.

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

That is, the transistor 1 and the input current source 2 are connected in series between the power supply Vl and the ground, the bases of the transistor 3 and the transistor 5 are connected in common, the emitter of the transistor 6 is led out to the output current terminal 7, and the base of the transistor 40 is connected in series. Connected to input current source 2.

In this configuration, the base currents of transistors 1 and 6 become equal due to the mirror circuit made up of transistors 3 and 5. Therefore, the output current will be equal to the input current. Here, when the output is open, that is, when the emitter of the transistor 6 is open, the base current of the transistor 50 is extremely small considering the emitter current of the transistor 3.

Therefore, the current increase through the power supply v2+ is negligible.

〔Effect of the invention〕

As described above, the present invention can provide a current source circuit with a simple circuit configuration that does not cause unnecessary current to flow even when the output is OFF.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional current mirror circuit. 1.3, 4, 5, 6, 9, 10.11...transistor, 2.8...input current source.

Claims (1)

[Claims] The first one has an emitter that receives an input signal and a collector that is grounded.
a first transistor with a polarity, a second transistor with a second polarity whose emitter is grounded and whose collector is connected to the base of the first transistor; and a second transistor with the same polarity as the second transistor and whose bases are connected to each other. , a third transistor whose emitter is grounded, a fourth transistor of a second polarity whose base receives the input signal and whose emitter is connected to the base of the third transistor;
A current source circuit comprising: a fifth transistor having the same polarity as the transistor, having a collector grounded, a base connected to the collector of the third transistor, and an emitter led out to a current output terminal.