JPS5837719A - Constant current generator - Google Patents

Abstract

PURPOSE:To highly make a mirror ratio accurate and to highly make an output current stable, by taking one of outputs of a current mirror circuit as a reference signal and providing a negative feedback loop controlling an input power supply so that this reference signal can become a prescribed value. CONSTITUTION:The emitter of a transistor (TR) Qf for reference current generation is connected to a power supply 11 and the base is connected to the base of other TRs Q1-Q3. A collector current of the TRQf is a reference current and inputted to an input terminal 15 of a control circuit 14. The control circuit 14 compares a reference input If of a terminal 15 with a reference input II of a terminal 16 and controls an output of a terminal 17, i.e., an input current IOT of a current mirror circuit so that both the inputs are made coincident. In using an element of the same characteristics as those of the TRs Q2 and Q3 for the TRQf, the reference current If and output currents I01 and I02 of the current mirror are equal to each other, and an output current of a constant value proportional to the input current II or an input voltage VI.

Description

DETAILED DESCRIPTION OF THE INVENTION This output W14 is %O for a constant current generator that generates a constant current proportional to the input voltage or input current.

Conventionally, this type of constant current generator has a current (two circuits), and its configuration is shown in Figure 1.
The operating principle is explained in detail in, for example, "Transistor Technology J" (January 1980 issue, pp. 249-251, published by CQ Publishing Co., Ltd., "Analog ICO Basic Circuit" @Chapter 2, published by Tokyo Electric University, Idataka Bureau, etc.). Therefore, a detailed explanation will not be given.pnp) Each of the transistors (pnp), ka, and Qao is connected to the power supply 11 of voltage VO@, and the transistors -, Qs
Each pre-coupling is a load, and each IJ is I! The transistor Qs OH collector is connected to the resistors R, O resistors all!
Input through 111 child I 54C1llfiiii, each trafuji
Karen Germany - The number 1 in the circuit is a sufficient one-to-two ratio due to the influence of the RO base current, that is, Karen Germany -
It is difficult to obtain an input current, output current, and O ratio of 0111 degrees, and a base current flows through each base of the six 60 p to On the side, the base current is multiplied by the corresponding tri-diode IO current amplification factor and nine currents are output. ζζ
Assuming that the characteristics of each transistor are the same, what are the characteristics of each transistor? y
The resistor O - retata current is equal to O, but the force v)/
)-2 tm*o Since each base electric current fi1ms~1b- of the transistor #a also flows to the input terminal 13, the actual O
Transis! - and the collector current of Qj, that is, the current (
2- each output current Io1. I・1 (Load Lt @L
While the input current lK flowing to the input terminal 13 is equal to the collector current of each transistor, the input current lK flowing to the input terminal 13 is equal to the collector current of the corresponding transistor current 1b1
Since ~1b. is added to the flow, it has a disadvantage that it is difficult to increase the N content of the Iller ratio.

(Conventional Karen) (2-1 The input of IIN has the same characteristics as a diode, and the voltage between the collector and the transistor of transistor Q1 is vo. The voltage of Q1 voltage 11 is va. The voltage fi setting resistor [7120 If the resistance is represented by R and the input terminal 130 is represented by vl, the input current II of the current-2-circuit is expressed by equation (1).

Iw = (Vae V (1@Ql
-Vl ) / B@ ”...=(1) Therefore, the input current 1. is affected by fluctuations in the power supply voltage v6゜.
・Since ql has temperature characteristics, the output voltage also fluctuates due to this influence, which has the disadvantage that stable current cannot be obtained. ・This invention aims to eliminate these disadvantages. ・Current-to-circuit By adding a negative feedback loop that controls the input voltage so that the outputs of 1)'j-reference signal and JisoO reference signal become predetermined values,
% (2 ratio is highly accurate and the output type mt is highly stabilized.) Figure 2 shows the first embodiment of ζO Yamei, and parts corresponding to those in Figure 1 are given the same symbols. In this invention, a transistor for generating a reference current is provided, and seven transistors (ivy is connected to the power supply 11, base tz and other transistors Qt) are provided.
~ Connected to the base of the fairy tale. The collector current of the transistor is a reference current and is input to the input terminal 15 of the control circuit 14.

The control circuit 14 compares the reference input of the terminal 1B and the reference input of the terminal 160, and outputs the output of the terminal 17 so that both inputs match, and inputs the input voltage of the current error circuit #IX.! After explaining the ζO operation below, the control circuit 14 controls the input terminal I
SO input voltage 111x (or input voltage Vt) and reference voltage R
If, the input voltage fiIr (or input voltage Vt
) is larger than the reference current If by p4, the output current l·! is absorbed by the output terminal 17 of the control circuit M14. As a result of this control, the reference current If increases, and conversely, the input current ! ! (or input voltage V1) is the reference current! ! If it is smaller than , the control vA voltage 140 reduces the output current Iot absorbed by the output terminal 17, and as a result of the control, the reference current ! The slag decreases, and eventually the input voltage fiIt (t or input voltage V
t) and the reference current! f is controlled to match.

Here, if an element with the same characteristics as the transistor Qs is used for the transistor Qf, then in the explanation of FIG. Based on the same principle, the collector currents of the p transistors Qf, Qs, and QsO, that is, the reference current If, and the output current I of the current transistor
os e Ion is equal to p, eventually transistor Q1
characteristics, as well as the transistor Qf, Qs = Ql
The input voltage 111t or the constant voltage proportional to the input voltage v [0 output current I@I
Zero or less control circuit 1 that can obtain e Its
4, the constant current generation will be explained. In FIG. It is grounded, the output side is connected to the terminal 17 through the current initiation resistor @21 of the resistor R1 as required, and the 1 inverting input 1m is connected to the terminal 16 wk.

Next, the operation will be explained.The control circuit 14C) The input voltage Vi is applied from the input terminal 13 to the terminal 16, while the reference voltage RI
f is supplied to the control a input terminal 14 and reference input terminal 15, and the control t
The terminal terminal 1 is connected to the earth via the O return resistor 19 in the m circuit 4. The voltage drop generated across the feedback resistor 19 is inputted to the non-inverting input side of the operational amplifier 18. If the input voltage Vt is higher than the voltage drop across the feedback resistor 19, the output of the operational amplifier 18 will decrease. The voltage applied between the collector and the output terminal of the transistor Q1 increases, and eventually the output chamber I! of the control (b) I114 increases. IT increases and with this the transistor Qf e Qs * Qs O:
x collector current also increases, and the collector current of transistor QfC), that is, the feedback current 1f (D increases, the feedback resistance @1
90 also increases the voltage drop across both ends, and therefore the O potential on the non-inverting input side of the operational amplifier 14 increases, and this operation becomes negative feedback, so if the gain of the operational amplifier 180 is large enough, the input voltage v
Equilibrium occurs at the point where the voltage drops across 1 and feedback resistor 19 are equal. This Heisei 111 Qin case can be expressed mathematically as Vi Kan Rf-If ・・・・・・・・・・・・・・・・・・
−・・・・・・・・・・・・・・・−・−・−・・・・・・・
・−・(2) becomes, and if you transform this, If −Vi / Rf ・−・−・−・・−・−・
−・−・−・−・・−−−−−−−・・・・−・・−・
-+3), and (1Iat) is a constant constant current proportional to the input voltage O feedback current and the output voltage @Iat and! @Maro is obtained.

The reference voltage RIf is transistor I so that the pfI is clear according to formula 3.
It can be seen that since the term of the retata/eitzta related voltage vc@ of Q> is not included, the fluctuation of the output power R due to the fluctuation of VaeQtO, which was a problem in the conventional circuit, does not occur.

In this IK example, since both input potentials of the operational amplifier 1ll) are controlled to be equal, the input impedance of the control circuit 14 can be made very high.

FIG. 4 shows the case where the input of the embodiment is voltage
This is an example in which the input voltage at the input terminal 130 is converted to a voltage by terminating it with the termination resistor 22 and applied to the operational amplifier [11B. It is similar to the embodiment shown in Fig. 3. In Fig. S and Fig. 6, the transistor is in a single current direction.
In order to be able to handle alternating current input signals from No. 1 +, which can only be handled by the circuit, a means for passing a predetermined bias current through the Cullen German circuit was added.

That is, in FIG. 6, the feedback resistor 19C>the ground side is connected to the negative voltage V.
...The relational expression between the input voltage v1 and the reference current If in the embodiment of the 9th % of the top % which is terminated to the O power supply 23 is v
1■Rf・xl −v・・ If we transform this, If = (1/Rf) (vt + V**)
・−=”−・(4) Therefore, it is possible to realize the superposition of the bias current V··/Rf. In FIG. 6, the current supplied to the feedback resistor 19 is changed from the reference current If to the constant current source 2.
4, and the relational expression between the input voltage v1 and the reference current If is v4-Rt (If-In), and if this is transformed, If'' (Vi/Rf) + In
.=””− .=” . . . (5) Both embodiments can supply a predetermined bias current.

Figure 7 shows an example configured as a current input type with low input impedance - Each transistor IQ1 to Qs, Q
ft! The terminal 16 is connected to the non-inverting input side of the operational amplifier 18 within the control circuit 14, and a constant potential is given to the inverting input side, and the feedback The resistor 19 inputs the input current to the omitted input terminal 13! ! flows in, and its input current I! If is larger than the reference current If flowing through the reference current If, the potential of the inverting input terminal O of the operational amplifier 180 increases, and as a result, the output potential of the operational amplifier 180 increases, and the current flowing through the transistor Q1 increases. In response to this, the collector current of transistors Qt, Q and Qs increases, and the current flowing through the collector of transistor Q+ is applied as a reference current to the non-inverting input of operational amplifier 180 in control circuit 14. It acts in the direction of drawing out the current from the input current applied to the input terminal 13, and C becomes a negative feedback operation. Therefore, if the gain of the operational amplifier 6618 is sufficiently loud, the input current!
X and reference current! An equilibrium state occurs at the point where f is equal, and if the transistors Qf4 and QsO characteristics are equal,
The current values of the currents IH* If* Iat qIos become equal. The voltage Va connected to the inverting input terminal of the operational amplifier 16180 is a voltage source that determines the potential of the input terminal 160 of the control circuit 14, and the operating voltage of the transistor Qf. In the case shown in FIG. 8, when it is necessary to guarantee the negative power supply voltage v0. The operating voltage of the transistor QtO is guaranteed by connecting the power supply 26 of the transistor QtO to the common terminal of the current transistor, that is, to the terminal side of each transistor.

In the embodiments shown in FIGS. 7 and 8, the input impedance is 8? if the potential of the non-inverting input terminal of the operational amplifier 6180 is 8?
11 Due to the power of the earth, p operation increases @41180 Since it is fixed to the voltage of the inverting input terminal, it is very low. Therefore, for example, as shown in FIG. 9, by inserting a resistor 8627 with a resistance of R1 between the input terminal 16 of the control circuit 14 and the inverted input terminal of the operational amplifier 18, it is possible to cope with the p voltage input. In addition, in the same way as in the addition in an inverting amplifier using a well-known operational amplifier, as shown by the broken line in FIG.
It is also possible to add the bias voltage RIl from the constant current source 28 to the operational amplifier 18C) by using the addition function of 6 and e as shown in Fig. 10. It is also possible to set a bias current to each transistor by supplying it to the input terminal.〇As is clear from the above explanation, according to Kooia@, the characteristics of the input O transistor IQ1 of the current I2 circuit Therefore, as shown in FIG. 11, in the fifth EOfA embodiment, the transistor Q1 is removed and the control Vm
It is also possible to connect between the 0 terminal 1 terminal and the power supply 11, and replace the connection point with the bases of the transistors Qs, Qs, and Qf.
1** It is also possible to apply it to all of the discharge side.

Note that the resistance width 29 can be selected depending on the requirements for frequency characteristics, etc. The transistor in the above explanation is not limited to bipolar elements, but it is also possible to use field effect elements, etc. current (improved connection in the two circuits, e.g. inserting a resistor on the side of the output transistor, connecting the plug to the output transistor
It is also possible to apply the addition of an atto-tuned transistor to the present invention, and 1) Go's technique of setting the input/output current ratio based on the area ratio of transistors can also be applied in the same way.

As explained above, the present invention has the advantage of generating a constant current that is accurately proportional to the input signal and operates stably. The O embodiment in Figure 3 has the advantage that it is proportional to the input voltage*, can generate a constant current, and can obtain a high input impedance.
, the embodiment of FIG. 4 can generate a constant current proportional to the input current. Figure 5 01! In this embodiment, a predetermined O bias is applied to each transistor I, but the bipolar O input signal can be handled by O, and the OS example shown in Figure 6 provides another means for obtaining the same effect as the Ig4 Figure O embodiment. The advantage of the embodiment shown in Fig. 7 is that it can generate a constant current R proportional to the input current and provide a low input impedance.The embodiment shown in Fig. 8 fixes the potential of the input terminal to the earth ratio λ. There are 6 advantages that can be achieved・Part s
rlAo*The example is a constant current a proportional to the sum of the double-flow side input signals.
・The embodiment shown in FIG. 11 has the advantage of being able to control the number of transistors. Some 0

[Brief explanation of the drawing]

[Figure 1 is a connection diagram #g2 showing a conventional current two circuit.
The figure is a connection diagram showing an example of the basic configuration of this example, and FIGS. 3 to 11 are connection diagrams showing specific embodiments of the invention. 14: Control circuit, 15: Reference input of the control circuit. 16: Reference input of the control circuit, 17: Output of the control circuit,!
f: Reference voltage R* Qse Qse Qse Qf:
) register, 18: operational amplifier, 19: feedback resistor. 22: Final 111 resistance% 11.23.25.26: Power supply voltage 4 IoT @ IoT: Output current,! 4.28
:jlij current source s Lt @ L@ : Load. Patent applicant: Takashi Kusano, agent of Nippon Telegraph and Telephone Company

Claims (1)

[Claims] (1) Input a current Z2@ path having multiple outputs and one of its current error circuit IIO outputs as a reference signal, and compare the SoO reference signal and the input signal. In the direction where both signals match
A constant current generator equipped with a control circuit for controlling the IO input current tm.