JPS60100809A - Voltage/current converting circuit - Google Patents

Abstract

PURPOSE:To ensure the satisfactory voltage/current conversion over a wide current range by combining two PNP and NPN transistors (TR) and supplying the same current to both TRs from a current mirror circuit. CONSTITUTION:A resistance R is connected between the common-connected base and collector of a PNP TRQ1 and an earth, and the emitter of the TRQ1 is connected to the emitter of an NPN TRQ2. The base of the TRQ2 is connected to the base and the collector of an NPN TRQ3. The emitter of the TRQ3 is connected to the emitter of a PNP TRQ4. Then a current mirror circuit is connected to the collector of the TRQ2 as well as to the common-connected base and the collector of the TRQ3. The voltage V is impressed between the base and the collector of the TRQ4. Thus the output current has no change due to temperatures. In this way, the satisfactory voltage-current conversion over a wide current range is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a voltage-to-current conversion circuit that converts a voltage input into a current output.

Background technology and its problems A simple and basic voltage-current conversion circuit is as follows.
Something like the one shown in FIG. 1 can be considered.

This means that the emitter of the NPN transistor
PN to the collector of transistor X/
The commonly connected bases and collectors of the P-type transistors X and 2 are connected, and the PNP-type transistors X 3+
The base of transistor q is connected to the base of transistor
If the forward voltage between emitters is vBB/, the emitter voltage of transistor -VBI ■-...Song...Square/Tap (1) D current flows, and the same current is obtained from the collector of transistors Xj+X4'.

However, since the forward voltage between the base and emitter of the transistor changes depending on the temperature, the circuit shown in FIG. 1 has the disadvantage that the output current 2 changes depending on the temperature.

Therefore, a temperature-compensated voltage-current conversion circuit as shown in FIG. 2 can be considered. This means that the base of the NPNPNP transistor in the circuit of Figure 1 is PNPNP.
connected to the emitter of transistor N, and connected to the emitter of transistor
A resistor R/ is connected to the emitter of t, the collector is grounded, and a voltage ■ is applied between the base and collector.
If the base-emitter forward voltage of transistors X, X, is VI3Lt + VBB/, then the emitter voltage of transistors Xr, X/ is V+VB
gt, V-1-VBelbow-VBE/Nitoru, so the output current is V+VBg, t-VBg/I-□...Song...Song...(2) , is approximately equal to V/R.

However, even in the case of the circuit shown in Fig. 2, the difference in current density of the transistor Xj +
Due to the difference in the absolute value of VBB/ and the difference in temperature characteristics, the absolute value of the output current (2) varies, and the output current (2) changes depending on the temperature.

As a further improved voltage-current conversion circuit, one using a negative feedback amplifier as shown in FIG. 3 can be considered. That is, this is a circuit in which differentially connected transistors X t + The emitter voltage of becomes equal to the voltage V applied to the base of transistor xg, and the output current l becomes almost equal to V/R,
It is no longer affected by the forward voltage between the base and emitter of the transistor.

However, in the case of the circuit shown in Figure 3, the circuit is
There is a risk that it will become complicated or cause peaking or oscillation.

Purpose of the Invention In view of the above points, the present invention proposes a novel voltage-current conversion circuit that has a simple configuration and does not cause variations in the absolute value of the output current and does not change the output current due to temperature. It is something.

Summary of the Invention In the present invention, two PNP type transistors and two NP type transistors are used.
N-type transistors are combined and the same current is supplied to each transistor by a current mirror circuit to absorb the absolute value and temperature characteristics of the forward voltage between the base and emitter of the transistors.

Embodiment FIG.
NPN-type second transistor QJINPN-type third transistor Q3 and PNP-type second transistor Q
<=, PNP-type transistors Qj+Qg, and PNP-type transistors Q and 7+Qg, respectively, are formed.

1st. The bases and collectors of the third transistors Q/, QJ (7) are commonly connected, respectively, and the first... The third transistors Q/ and QJ each have a diode configuration, and a resistor R is connected between the base and collector of the first transistor Q/ and the ground terminal of the integrated circuit/. The emitter is connected to the emitter of the second transistor Q,2, the base of the second transistor Qx is connected to the base and collector of the third transistor Q3, and the emitter of the third transistor Q3 is connected to the emitter of the second transistor Q4= The collector of the ≠-th transistor QII is connected to the ground terminal l.

The bases and collectors of the second transistor Qs are commonly connected, and the fifth transistor Qr has a diode configuration, and the collectors of the second transistors Q and 2 and the base of the sixth transistor Qg are connected to the base of the second transistor Qs. The collector of the sixth transistor Qg is connected to the base and collector of the third transistor Q3, and the emitters of the transistors Qj and Qa are respectively connected to the power supply voltage supply terminal 3 of the integrated circuit. are connected to the second and second transistors Q, t+Q
6 constitutes a current mirror circuit. transistor Q
The bases of 71 Q g are respectively connected to the base and collector of the j-th transistor Q3, and the emitters are respectively connected to the power supply voltage supply terminal 3, so that the transistor Q
7, Q, and r each form a current mirror circuit together with the j-th transistor Qs. Then, the input voltage supply terminal t is derived from the base of the ≠-th transistor Q<=, and the input voltage supply terminal ≠
and the ground terminal, that is, from the outside of the integrated circuit/
A voltage ■ is applied between the base and collector of the transistor Q<=.

In this circuit, transistors Q<=, Q3. The base-emitter forward voltage of Qx and Ql is vnB't, respectively.
+VnEJ r VBg, 2 + VBE/, then
At the emitter of the transistor Ql/, V + vBEl
'The voltage at the base and collector of transistor Q3,
Therefore, the base of transistor Q2 has V+VBB<z
+VREJ chisel pressure, t-runges, V+Vng+ on the emitter of Q, 2, voltage on +VB+q3-VBE, 2, V+ on the base and collector of transistor Ql
VBgg +Vag3-VBE, 2-VBn/(7) voltage forces are obtained, respectively, and the voltage at the base and collector of transistor Q/ is converted into a current by resistor R, and the collectors of transistors Q/, Q, and 2 have no current. current flows,
The same current is obtained in the collector of transistor Q 71 Q i.

Here, transistors Q3 . The same current I flows through the collector of Qg, so VHB/-VB
g<z+VBBj−VBEJ, and the absolute value of the forward voltage between the base and emitter of the transistor and the temperature characteristics are both canceled, and ■■=100 ・・・・・・・・・・・・・・・・・・・・・・・・
. . . (4) Therefore, variations in the absolute value of the output current I and changes due to temperature do not occur. Even if the voltage V applied from the outside of the integrated circuit/ changes, the current flowing through transistors Q/, Q, 2 and transistor Q
The current flowing through J IQ<= changes equally, and VBg/
2■BBψ.

VBI! 2=VBE,? relationship is maintained.

By the way, in the case of the example shown in Figure ≠, when the voltage V is zero, the current ■ does not flow and no voltage is applied to the base of the transistor Q2, so even if the voltage ■ increases thereafter, the current I
may not flow and the circuit may not start.

In view of this point, the example in Fig. 5 is a case where a startup circuit is added to the circuit in the example in Fig.
o is formed, the base and collector of the transistor Q10 are commonly connected so that the transistor Q10 has a diode configuration, the emitter of the transistor Q9 is connected to the base and collector of the first transistor Q/, and the collector is connected to the λ-th transistor Qλ. The base of the transistor Q10 is connected to the base and collector of the transistor Q10, and is also connected to the power supply voltage supply terminal 3 via the resistor R3, and the emitter of the transistor Q10 is connected to the ground terminal ! via the resistor R4=. connected to.

In this circuit, when no current flows through transistors Q/, Qy, transistor Q10
Current flows. Even if the current flowing through transistor Qp is very small, transistor Q3. QI1. Since current flows through the transistors Q and 2, even when the voltage increases from zero, voltage is always applied to the bases of transistors Q and 2.
The circuit starts up. By keeping the base voltage of the transistor Q9 low within the necessary range, the transistor Q9 is cut off after startup, and the circuit operates in the same way as the example circuit shown in Figure 1.

FIG. 4 shows yet another example of the voltage-current conversion circuit of the present invention.
Transistors Q/~Q, l- are all made of the opposite conductivity type as in the example of Figure ≠, so that transistors Q1 . The collector of t is connected to the power supply voltage supply terminal 3, and the transistor Qr
The emitters of -Qtr are connected to the ground terminal λ, and resistors R5 and R are connected between the power supply voltage supply terminal 3 and the ground terminal l within the integrated circuit, and the base of the transistor Q<= is connected to the resistor. It is connected to the connection point of Rj and R6, and a voltage V is applied between the collector and base of the transistor QII inside the integrated circuit/, and a terminal is led out from the base and collector of the transistor Q/, so that the integrated circuit/ A resistor R is connected between the terminal 3 and the power supply voltage supply terminal 3 externally.

In this example as well, transistors Q/, Qx and transistor Q J IQ4t
A current of ■=100 flows through the transistor Q 71Q,! −
The same current can be obtained. In this example, no start-up circuit is required since the voltage V is initially provided within the integrated circuit.

Effects of the Invention According to the present invention, a resistor R is connected between the commonly connected base and collector of the first transistor Q/ and a terminal to be connected to one end of the power supply, and the emitter of the first transistor Q/ is connected to the emitter of a second transistor Q,2 of a conductivity type different from that of the first transistor Q, and the base of the second transistor Q,2 is connected to the second transistor Q,2.
is connected to the commonly connected base and collector of the third transistor Q3 of the same conductivity type as the third transistor Q3.
The emitter of the transistor Q is connected to the emitter of the second transistor of the same conductivity type as the first transistor Q, and the base and collector of the second transistor Q, which are commonly connected to the collector of the second transistor Q, and the third transistor Q3 are connected to the transistor Qs. ,
Since a current mirror circuit consisting of Q6 is connected and a voltage is applied between the base and collector of the ≠th transistor Q<z, the absolute output current is Good voltage-to-current conversion is achieved over a wide current range without causing variations in value or changing the output current due to temperature.

[Brief explanation of the drawing]

7 to 3 are connection diagrams of an example of a possible voltage-current conversion circuit, respectively. FIGS. 7 to 6 are connection diagrams of an example of a voltage-current conversion circuit of the present invention, respectively. In the figure, Q/, Q,,! , Q3. Q is the first. Second. Third
The seventh transistors Qr and Qg are transistors forming a current mirror circuit. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A resistor is connected between the commonly connected base and collector of the first transistor and a terminal to be connected to one end of the power supply, and the emitter of the first transistor is connected to the first transistor.
Transistors and different conductivity types! is connected to the emitter of the second transistor, and the base of the second transistor is connected to the emitter of the second transistor! The emitter of the third transistor is connected to the commonly connected base and collector of a third transistor of the same conductivity type as the first transistor, and the emitter of the third transistor is connected to the emitter of a third transistor of the same conductivity type as the first transistor. A current mirror circuit is connected to the commonly connected bases and collectors of the collector of the second transistor and the third transistor, and a voltage is applied between the base and collector of the ≠ third transistor. conversion circuit.