JPS6074806A - Constant current bias generating circuit - Google Patents

Abstract

PURPOSE:To avoid the effect of the variation of the power supply voltage by constituting a constant current bias generating circuit with four transistors and two resistances and to secure the specific conditions for the relation between the emitter areas of said transistors. CONSTITUTION:A constant current bias generating circuit consists of transistors (TR) Q1-Q4 and resistances R1 and R2. The TRs Q1-Q4 have the same emitter area and the TRQ4 has its emitter area which is (n) times as much as those of other TRQs. It is decided that the current value of the R1 and TRs Q1 and Q2 is equal to I1 and the current value of TRs Q3 and Q4 and the R2 is equal to I0 respectively as long as the current amplification factor of each TR is satisfactorily large. The relation shown by an equation I is obtained since the saturated current value is proportional to the emitter area, where (k), T and (q) show the Boltzmann constant, absolute temperature and electronic charge respectively. In the equation I the output current I0 has no relation with the output current I1. Therefore it is possible to obtain a stable constant output current I0 regardless of the power supply voltage and the resistance R1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a constant current bias generation circuit, and more particularly to a constant current, current bias generation circuit that is not affected by fluctuations in power supply voltage.

[Prior art and problems]

Conventionally, a circuit as shown in FIG. 1 has been used as a constant current bias generating circuit. The circuit of FIG. 4 includes transistors Qs, Q2 and a resistor R.

It consists of In the circuit of FIG. 1, if the emitter area of the transistor Q2 is designed to be n times the emitter area of the transistor Qs, then Io=n■. The current It through transistor Ql is equal to the supply voltage V.

c, base emitter of transistor Q1 'IEEVBH
It is determined by the following equation by R, R, and resistance R.

11=(vCC-vBEl)/R1 Therefore, the output current I. is the following equation (1), regardless of the load.By the way, this current value varies depending on the power supply voltage, so
There is a problem in that it is affected by fluctuations in power supply voltage.

[Purpose of the invention]

In view of the problems of the prior art described above, the object of the present invention is to
An object of the present invention is to provide a constant current bias generation circuit that is not affected by fluctuations in power supply voltage.

[Structure of the Invention] In order to achieve the above object, the present invention includes a first resistor, first and second transistors, and a current A constant current bias generation circuit having a second resistor, third and fourth transistors connected in series between an output terminal and the negative power supply, the first resistor connected to the positive power supply and the a first transistor connected between the collectors of the first transistor, the first transistor's pace being connected to the collector thereof, and the emitter of the first transistor being connected to the collector of the second transistor; an emitter of the third transistor is connected to the negative power supply, a collector of the third transistor is connected to the current output terminal, a pace of the third transistor is connected to a pace of the first transistor, and a collector of the third transistor is connected to the current output terminal; The emitter of the transistor is connected directly or through the second resistor to the collector of the fourth transistor, and the fourth
The pace of the transistor is connected to the collector of the second transistor, the pace of the second transistor is connected to the collector of the fourth transistor, and the emitter of the fourth transistor is connected to the collector of the second transistor. or directly connected to the negative power supply, the emitter areas of the first and second transistors and the emitter area of either the third or fourth transistor are the same; There is provided a constant current bias generation circuit characterized in that the emitter area of the other transistor of No. 4 is n times larger than that of the other transistors.

[Embodiments of the invention]

The current noise generating circuit according to the present invention will be explained below with reference to the drawings.

FIG. 2 shows a constant current bias generation circuit as a first embodiment of the present invention. The constant current bias generation circuit shown in FIG. 2 includes transistors Q1 and Q2.

It consists of Qs lQ4 and resistor RI I R2.

The emitter areas of the transistors Q1 *Qt +Qa are the same, and the emitter area of the transistor Q4 is formed to be n times larger than that of the other transistors.

Assuming that the current amplification factor of each transistor is large enough,
Resistor R1,) The current value flowing through transistor Qt-Qs is equal to
The value of the current flowing through 2 is . can be considered to be equal to It is represented by the pace emitter voltage VBmci of each transistor. Here, l(: yl? Lutzmann constant, T: absolute temperature,
q: electron charge, q; l: saturation current, current. The collector potential VC of the transistor Q is VC"v111C1+
vBE4+IOR2=vBI2+vBE5, and it holds true that the saturation current value is proportional to the emitter area. Therefore, kT I o-R2,tn n is obtained. This output current IO is independent of 11, and therefore a stable constant current output IO that is not affected by power supply voltage VCC and resistor R8 is obtained.

FIG. 3 shows a constant current bias generation circuit as a second embodiment of the present invention. The circuit of Fig. 3 consists of transistor Q2
The area of the emitter of transistor Q2 is twice that of other transistors, and resistor R3 is connected to the emitter of transistor Q2 and transistor Q4.
The circuit differs from the circuit shown in FIG. 2 in that it is connected between the collectors of the circuit. The output current of the circuit of FIG. 3 is the same as that of FIG. 2 and is not affected by the power supply voltage.

〔Effect of the invention〕

According to the present invention, a stable constant current bias generation circuit that is not affected by power supply voltage fluctuations can be provided.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional constant current bias generation circuit, FIG. 2 is a circuit diagram of a constant current bias generation circuit according to a first embodiment of the present invention, and FIG. 3 is a circuit diagram of a conventional constant current bias generation circuit according to a first embodiment of the present invention. FIG. 2 is a circuit diagram of a constant current bias generation circuit as an example of FIG. (Explanation of symbols) Ql +Q* *Qa #Q4:) Ranister ~R1
, R2: resistance.

Claims (1)

[Claims] A first resistor, first and second transistors connected in series between a positive power source and a negative power source, and a second resistor connected in series between a current output terminal and the negative power source. , 3rd
and a fourth transistor, the first resistor is connected between the positive power supply and the collector of the first transistor, and the first resistor is connected to the collector of the first transistor. , the emitter of the first transistor is connected to the collector of the second transistor, the emitter of the second transistor is connected to the negative power supply, and the collector of the third transistor is connected to the current output. the third transistor pace is connected to the first transistor pace, and the third transistor pace is connected to the first transistor pace;
The emitter of the transistor is directly connected to the collector of the fourth transistor through the second resistor, the base of the fourth transistor is connected to the collector of the second transistor, and the emitter of the fourth transistor is connected directly to the collector of the fourth transistor through the second resistor. The pace of the transistor is connected to the collector of the fourth transistor, the emitter of the fourth transistor is connected to the negative power supply via the second resistor or directly, and the emitter of the fourth transistor is connected to the negative power supply through the second resistor. and the emitter area of either the third or fourth transistor are the same,
A constant current bias generation circuit characterized in that the emitter area of the other of the third or fourth transistor is n times larger than that of the other transistor.