JPS6366066B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to semiconductor integrated circuits.

Conventionally, in a current source circuit as shown in Fig. 1, the first
The area of the emitter 3 of the transistor 1 and the resistance 5
Based on the value of , the area of the emitter 4 of the second transistor 2 is multiplied by n, and the value of the resistor 6 is set to 1/n, and the emitter current flowing through the first transistor 1 is n.
The structure is such that twice the emitter current flows through the second transistor 2. For this reason, it is necessary to align the shape and direction of the transistors and achieve matching between elements.
Furthermore, considering the temperature distribution, two potential transistors 2' and 2'' are laid out on both sides so that the emitter area is n/2 times the emitter area of the first transistor 1, as shown in Figure 2. In this way, the second transistor 2 of FIG. 1 is realized, and the emitters 4 of the second transistors 2' and 2'' are
and 4' are wired using through holes 10 and 11 to form a second transistor with an emitter area n times larger. Wirings 50 and 51 cross the resistors 5 and 6. In this case, the wiring for the emitters 4 and 4' of the transistors 2' and 2'' is such that the emitter 4 of the second transistor 2' is directly connected to the resistor 6 by a single layer wiring, and a through hole 10 is provided in the middle of the first layer wiring. A through hole 11 is provided in the emitter 4' of the transistor 2'', and the through holes 10 and 11
Connect with two-layer wiring. The first transistor 1 is directly connected to the resistor 5 by a single layer wiring. FIG. 3 shows an equivalent circuit of the layout of FIG. 2, taking into account the resistance of the through holes.

In Figure 3, the voltage drop between the ends 40 and 41 of resistors 5 and 6 and the emitters 3, 4, and 4' of each transistor, that is, the voltage drop due to the through-hole resistor V _th and the voltage drop due to the transistor V _BE , is expressed as V _BEr. year,
Also, the voltage between terminals 8 and 7 is V _B , the emitter current of the first transistor 1 is n/2 times the emitter current of the first transistor 1, the emitter current of transistors 2' and 2'' is n/2 of the emitter current of the first transistor 1, and the resistor 5 is , 6 are the resistance values R and R/n, and the through-hole resistance is _R th.The transistor V _BE is as follows: V _BE of transistor 1 = V _B −R ₅ ×I V _BE of transistor 2′ = V _B −2R ₆ × V _BE of n/2 transistor 2''=V _B -(2R6+R _th 22+R _th 23)×nI/2. From this, V _BE of the first transistor 1
It is clear that the voltage drop of the through-hole resistor R _th is included in the V _BE of the transistor 2''. In this way, due to the voltage drop of the through-hole resistor, V _BE decreases and the current increases by n times. The drawback was that the ratio could not be achieved with high precision.

It is an object of the present invention to provide a circuit that solves these problems and obtains a highly accurate current ratio by equalizing voltage drops caused by through-hole resistors and equalizing V _BE .

In the semiconductor integrated circuit of the present invention, the voltage drop from the emitter of the first transistor through which a reference current flows to the first reference potential point is reduced from the emitter of the second transistor through which a current n times the reference current flows to the first or second transistor. By increasing the number of through holes that enter between the emitter of the first transistor and the second reference potential point to n times the number of through holes that enter between the emitter of the first transistor and the first reference potential point, It is characterized in that the potential drop is equal to the potential drop to the first or second reference potential point.

The present invention will be explained in detail below using the drawings.

FIG. 4 is an embodiment of the layout for the circuit of FIG. 1 according to the present invention.

In FIG. 4, the emitter 3 of the first transistor 1 is provided with a through hole 12, and connected to the resistor 5 through two-layer wiring and a through-hole 13 through one-layer wiring, and the emitter current of the first transistor 1 is n times The transistor through which n/2 flows is divided into two transistors, a second transistor 2 and a third transistor 2', through which n/2 emitter current flows. Wiring 5
Since 0,51 crosses resistors 5,6, its emitter 4
and 4' are n/2 times the number of through holes 10,1
1. It is connected to n/2 times as many through holes 14 through two-layer wiring, and connected to the resistor 6 through one-layer wiring. This layout is shown in an equivalent circuit as shown in FIG. Now, let the resistance values of through-hole resistors 20 to 25 be r _th , and the resistance values of resistors 6 and 5 be R,
R/n, the voltage at terminal 8 and terminal n is V _B , and the emitter current 33 of the first transistor 2'' is n/2I. To explain FIG. 5, consider FIG.
In FIG. 6, a is an equivalent circuit of wiring connected to the emitter 3 of the first transistor 1 serving as a reference. b shows an equivalent circuit of wiring connected to the emitter 4 of the second transistor 2. Here, the potential drop V _th due to the through-hole resistance is V _tr 31 in a of Fig. 6.
Comparing with V _tr 30 in b of Fig. 6, V _tr 31 in a in Fig. 6 is V _tr 31 = r _th ×I, and V tr 30 in b in Fig. 6 is V _{tr 30} = r _th × 2/n×nI/2=r _th ×I, and the voltage drop V _tr due to the through-hole resistance is similarly equal for V _tr 30' and 31'. This potential drop is due to the through-hole resistance when using from the first layer to the second layer 30, 31, and due to the through-hole resistance when using from the second layer to the single layer 30', 3
1', and the potential drop of the through hole, which has an effect as if to reduce V _BE , is the sum of these two, and becomes V _tr 35 and 36. The sums of voltage drops V _tr 35 and 36 are equal because V _tr 30, 31 and 30', 31' are equal. Here the fifth
Returning to the diagram again, the voltage drop 35 between the emitter 3 of the first transistor 1 and the terminal 40, which serves as a reference, and the potential drop 36 between the emitters 4 and 4' of the second transistor 2' and the third transistor 2'' and the terminal 41 Since the current flowing through each through hole is also the same, the heat generated by the through hole itself is also constant.

As explained in detail so far, the same voltage drop occurs between the emitter of each transistor and the resistor as between the emitter of the reference transistor and terminal 40, so if the emitter current is n times larger, the error in the through-hole resistor occurs. By passing the same current through one through hole, the heat generation becomes uniform, so the change in resistance due to the current is also the same, and there is no effect on current matching due to the insertion of through holes. . For this reason, there is an effect that it is possible to easily obtain a circuit that obtains n times as much current.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing an example of a current mirror.
2 is a partial plan view showing a conventional semiconductor integrated circuit shown in FIG. 1, FIG. 3 is an equivalent circuit diagram of FIG. 2,
4 is a partial plan view showing a semiconductor integrated circuit according to an embodiment of the present invention shown in FIG. 1, FIG. 5 is an equivalent circuit of FIG. 4, and FIG. 6a is a wiring connected to the emitter of the first transistor. The equivalent circuit of
The equivalent circuit of the wiring connected to the transistor is shown. 1, 2, 2'...transistor, 3, 4, 4'...
...Emitter, 5, 6...Resistor, 7, 8...Terminal,
10, 11, 12, 13, 14... Through hole, 20, 21, 22, 23, 24, 25... Through hole resistance, 30, 31... Voltage drop due to through hole, 32, 33... Emitter current, 3
4...Two-layer wiring, 35, 36... Voltage between emitter and resistor, 50, 51... Aluminum wiring.

Claims (1)

[Claims] 1 In a semiconductor integrated circuit using multilayer wiring, the voltage drop from the emitter of the first transistor through which the reference current flows to the first reference potential point, and the reference n
The voltage drop from the emitter of the second transistor through which twice the current flows to the first reference potential point is
The number of through holes inserted between the emitter of the second transistor and the first reference potential point is made equal by n times the number of through holes inserted between the emitter of the second transistor and the first reference potential point. A semiconductor integrated circuit characterized by: