JPH0587148B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a differential amplifier circuit realized by a semiconductor integrated circuit. In particular, it relates to improvements in layout when symmetrically arranging constituent elements of a differential pair.

〔overview〕

A conductor area for the power supply potential is provided approximately in the center of the circuit,
In a differential amplifier circuit in which circuit elements on the positive phase side and negative phase side are arranged symmetrically with respect to this area, the above conductor area is hollowed out and at least part of the elements serving as a common current source is placed here. This further improves the balance characteristics.

[Conventional technology]

Differential amplifier circuits are widely used as amplifier circuits and current switching circuits in linear integrated circuits. In integrated circuits, transistors and resistance values made on the same silicon chip are essentially the same. Therefore, circuits that require a balanced circuit design of transistors and resistors, such as differential amplifier circuits, are suitable for implementation with integrated circuits. Furthermore, differential amplifier circuits can amplify from direct current to high frequencies, and have recently come to be used in the ultra-high frequency range from hundreds of megahertz to gigahertz.

Figure 4 shows the basic circuit of a differential amplifier circuit, which is composed of transistors Q ₁ , Q ₂ and resistors R ₁ , R ₂ , R ₃ , with the base of transistor Q ₁ connected to input terminal 1,
The base of transistor Q ₂ is connected to input terminal 2, the collector of transistor Q ₁ is connected to output terminal 3, the collector of transistor Q ₂ is connected to output terminal 4, and the resistor
One end of R ₁ is connected to the collector of transistor Q ₁ and the other end is connected to the high potential side power line 5. One end of resistor R ₂ is connected to the collector of transistor Q ₂ and the other end is connected to the high potential side power line 5. and one end of resistor R ₃ is Q ₁
and the other end is the low potential side power supply line 6 to the emitter of _Q2 .
It is connected to the.

Conventionally, when designing the balance of a differential amplifier circuit, an integrated circuit has been designed by taking into consideration the balance of transistors and resistors, and the balance of differential positive-phase and negative-phase signal propagation delay times. Figure 5 shows
A conventional example of a layout diagram for realizing the circuit diagram of FIG. 4, which is a basic circuit of a differential amplifier circuit, on a silicon chip is shown. The points considered in the balance design in Fig. 5 are the transistors Q ₁ ,
Q ₂ , resistors R ₁ and R ₂ are arranged vertically symmetrically, the input signal line 11 and the input signal line 12 have the same length, and the output signal line 13 and the output signal line 14 have the same length.
The purpose is to make the lengths of the two equal. In the transistors Q ₁ and Q ₂ in Fig. 5, C indicates the collector, B indicates the base, and E indicates the emitter.
The same applies to B and E.

To explain the conventional example in FIG. 5 in more detail, a low potential side power line 6 runs in the center, and high potential side power lines 5 and 7 run above and below it, respectively.
A transistor Q ₁ and a resistor R ₁ are arranged between the low potential side power line 6 and the upper high potential side power line 5, and a transistor Q ₂ is arranged between the low potential side power line 6 and the lower high potential side power line 7. and a resistor R ₂ are arranged, and a resistor R ₃ is arranged on the transistor Q ₁ side. in this way,
Since the resistor R ₃ is placed on the transistor Q ₁ side, comparing the wiring lengths of the connecting wire 15 between the emitter of the transistor Q ₁ and the resistor R ₃ and the connecting wire 16 between the emitter of the transistor Q ₂ and the resistor R ₃ , , the latter connection wiring 16 is longer. Connection wiring 1
The wiring impedance (particularly the wiring parasitic capacitance) differs due to the difference in wiring length between the wiring 5 and the connection wiring 16.

[Problem that the invention seeks to solve]

In the conventional layout diagram shown in FIG. 5 mentioned above, the length of the signal lines from the input terminal to the output terminal is equal;
Moreover, the length of the signal line has become relatively short,
Since the lengths of the connection wiring 15 and the connection wiring 16 are different, there is a drawback that a balanced design of the respective wiring impedances cannot be realized. In particular, regarding the wiring impedance of the connection wiring 15 and the connection wiring 16, the parasitic capacitance that exists between the wiring part and the silicon substrate disturbs the balance of the differential amplifier circuit, which becomes a fatal drawback when the operating frequency exceeds several hundred megahertz. becomes. Therefore, in the balanced design of a differential amplifier circuit, it is necessary to fully consider not only the balance of transistors, resistance values, and wiring lengths of signal lines, but also the balance of parasitic capacitance of other wirings.

The present invention improves on this, and aims to provide a differential amplifier circuit that further improves the circuit balance state.

[Means for solving problems]

In the present invention, an elongated conductor region connected to the potential on one side of the power supply is provided approximately in the center of the circuit, and circuit elements on the positive phase side and negative phase side are arranged at approximately symmetrical positions with this conductor region as a border. In the differential amplifier circuit, at least a part of an element that serves as a current source for a current commonly applied to the circuit elements on the positive phase side and the negative phase side is arranged in an area provided by hollowing out the conductor region. It is characterized by

[Effect]

By arranging part or all of the circuit element that serves as a common current source for the positive phase side and the negative phase side in an area cut out within the conductor region, the circuit layout becomes symmetrical and the circuit element It is shielded by the conductor, so it will not be biased to one side.

〔Example〕

Next, the present invention will be explained using the drawings.

FIG. 1 is a layout diagram of an embodiment of the present invention. A conductor region 6 having a power supply potential on the low potential side is arranged in the center, and a part of the conductor region 6 is hollowed out to provide a non-wiring area 10. A resistor that commonly supplies current to the positive phase side and negative phase side within this area 10
R ₃ is placed. A positive phase side transistor of the differential amplifier circuit is connected between the conductor region 6 and the high potential side conductor 5.
Q ₁ and a resistor R ₁ are arranged, and a negative phase side transistor Q ₂ and a resistor R ₂ of the differential amplifier circuit are arranged between the conductor region 6 and the lower high potential side power supply line 7.

In this way, by hollowing out a part of the conductor region 6 to provide the area 10 and arranging the resistor R ₃ in this area 10, the transistors Q ₁ and Q ₂ and the resistors R ₁ , R ₂ , and R ₃ are made symmetrical. This realizes a balanced design for transistors and resistors, a balanced design for positive phase and negative phase regarding the length of the signal line from the input terminal to the output terminal, and a balanced design for the wiring 8 and 9 other than the input/output signal wiring. be done.

2 and 3 are circuit diagrams and layout diagrams of other embodiments of the present invention. Transistor Q ₁₀₂ ,
A differential amplifier circuit is configured by each element Q ₁₀₃ , Q ₁₀₄ and resistors R ₁₀₃ , R ₁₀₄ , and R ₁₀₅ .

As shown in FIG. 3, an area 104 is provided by hollowing out a part of the power supply conductor region 6 on the low potential side.
, a transistor common to the positive and negative phase sides
Q ₁₀₁ , Q ₁₀₄ and resistors R ₁₀₂ and R ₁₀₅ are arranged. 2 in the diagram
×R ₁₀₁ and 2 × R ₁₀₈ have resistance values of R ₁₀₁ and R ₁₀₈
It shows that each value is twice the value of .

〔Effect of the invention〕

As explained above, according to the present invention, the symmetry of the circuit arrangement is extremely good, and the common parts are shielded by the power supply conductor, so there is no biased influence on one side, and extremely good balance characteristics are achieved. can get.

[Brief explanation of the drawing]

FIG. 1 is a layout diagram of a differential amplifier circuit according to an embodiment of the present invention. FIG. 2 is a circuit diagram of a second embodiment of the present invention. FIG. 3 is a layout diagram of a second embodiment of the present invention. Figure 4 is a basic circuit diagram of a differential amplifier circuit. FIG. 5 is a layout diagram of a conventional differential amplifier circuit. 1, 2, 101, 102...input terminal, 3,
4,103...Output terminal, 5,7...Conductor of high potential side power supply, 6...Conductor region of low potential side power supply, 8,
9... Wiring, 10, 104... Area cut out, 11 to 16... Wiring, Q ₁ , Q ₂ , Q ₁₀₁ ~
Q ₁₀₈ ...Transistor, R ₁ , R ₂ , R ₃ , R ₁₀₁ ~
R ₁₀₈ ...Resistance.

Claims (1)

[Claims] 1. An elongated conductor region connected to the potential of one side of the power supply is provided approximately in the center of the circuit, and circuits on the positive phase side and negative phase side are located at approximately symmetrical positions with this conductor region as a border. In the differential amplifier circuit in which the elements are arranged, at least a part of the element that serves as a current source for the current commonly applied to the circuit elements on the positive phase side and the negative phase side is located in an area provided by hollowing out the conductor region. A differential amplifier circuit characterized in that: