JPH0513541B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an improvement in a semiconductor integrated circuit (IC) incorporating a multi-stage cascaded amplifier circuit, such as an audio amplifier circuit.

(b) Prior Art Conventionally, for example, in an IC that incorporates a large signal system output stage amplifier circuit 1 and a small signal system front stage amplifier circuit 2 connected in cascade as shown in FIG. For example, a method of providing independent earth pads for each to prevent the influence of
Described in No. 176217. In the same figure, 3 is an input terminal, 4 is an output terminal, 5 is a _Vcc terminal,
The input signal applied to the input terminal 3 is voltage amplified by the pre-stage amplifier circuit 2, and the current is amplified by the output stage amplifier circuit 1 consisting of SEPP (single-ended push-pull) to drive the load connected to the output terminal 4. It is configured as follows. When the output stage amplifier circuit 1 and the pre-stage amplifier circuit 2 share a common ground potential, a potential drop occurs in the ground wiring due to the signal current amplified by the output stage amplifier circuit 1, and this is returned to the pre-stage amplifier circuit 2. This causes problems such as oscillation.

FIG. 3 is a plan view showing an IC having such a structure, in which 6 is a semiconductor chip, 7 and 8 are first and second earth pads, and 9 and 10 are first and second earth electrodes.
Two channels of the circuit shown in FIG. 2 are incorporated into the surface of the semiconductor chip 6 by a predetermined process, and when the circuit is constructed, the transistors are surrounded and isolated by isolation regions. A first ground electrode 9 is provided to surround the output stage amplifier circuit 1, and is configured to immediately suck out the parasitic current of the output transistor that handles a large current by making ohmic contact with the isolation region below it. are doing. In addition, a second ground electrode 1 is provided near the front stage amplifier circuit 2.
0 is provided, and supplies a ground potential to the front stage amplifier circuit 2 electrically independently from the semiconductor chip 6. For the reasons mentioned above, independent first and second ground pads 7 and 8 are provided for the first and second ground electrodes 9 and 10, respectively, to serve as terminals for external connection.

(C) Problems to be Solved by the Invention However, in the conventional semiconductor integrated circuit, all of the parasitic current of the output stage amplifier circuit 1 and the pre-stage amplifier circuit 2 is sucked out only by the first earth electrode 9, so that the parasitic current is There is a drawback that a potential gradient occurs in the semiconductor chip 6, causing problems such as oscillation and parasitic thyristors in the front stage amplifier circuit 2.

(d) Means for Solving the Problems The present invention has been made in view of the above-mentioned drawbacks, and the output stage amplifier circuit 1 is formed in ohmic contact with the semiconductor chip 6 in the region where the front stage amplifier circuit 2 is formed. This is a semiconductor integrated circuit in which the drawbacks of the conventional semiconductor integrated circuit are greatly improved by providing a third ground electrode 11 that does not make ohmic contact with the semiconductor chip 6 in the region but extends over the semiconductor chip 6 and connects to the first ground pad 7. It provides:

(E) Effect According to the present invention, the parasitic current near the front stage amplifier circuit 2 can be immediately sucked out by the third earth electrode 11, and moreover, by connecting the third earth electrode 11 to the first earth pad 7. Therefore, the potential of the semiconductor chip 6 can be stabilized without affecting anything else.

(f) Examples Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a plan view showing a semiconductor integrated circuit of the present invention, in which 6 is a semiconductor chip, 7 and 8 are first and second earth pads, and 9, 10, and 11 are first to third earth electrodes. The circuit shown in FIG. 2 is fabricated on the surface of the semiconductor chip 6 by a predetermined process so that two channels are vertically symmetrical, and the transistors forming the front-stage amplifier circuit 2 and the SEPP of the output-stage amplifier circuit 1 are formed. The power transistors are surrounded and isolated by isolation regions. The individual transistors are connected to each other by electrode wiring so as to perform a predetermined function, and first and second ground pads 7 and 8, which are independent of each other for external connection, are arranged near the outer periphery of the semiconductor chip 6. be done. A first ground electrode 9 is in ohmic contact with the isolation region therebelow via the contact hole 12 so as to surround the region of the output stage amplifier circuit 1 of each channel.
is connected to the first earth pad 7 and is configured to immediately recover the parasitic current of the output stage amplifier circuit 1 which handles a large current. Further, a second ground electrode 10 that is electrically independent of the semiconductor chip 6 extends near the front stage amplifier circuit 2 and is connected to a second ground pad 8.

And the third earth electrode 1 which is a feature of the present invention
1 makes ohmic contact with the semiconductor chip 6 via the isolation region near the region where the pre-stage amplifier circuit 2 is formed, and crosses the region of the output stage amplifier circuit 1 without making ohmic contact with the semiconductor chip 6. and is connected to the first earth pad 7.

According to such a configuration, the parasitic current of the semiconductor chip 6 in the region where the front-stage amplifier circuit 2 is formed can be effectively sucked out by the third ground electrode 11, and furthermore, the parasitic current can be sucked out completely by the third ground electrode 11. I have nothing to give.

That is, the preamplifier circuit 2 is normally designed with a high gain, and it is necessary to avoid the ground potential becoming unstable due to the parasitic current sucked out.
The parasitic current in the region where the preamplifier circuit 2 is formed cannot be sucked out by the second earth electrode 10. On the other hand, if the first earth electrode 9 is extended and ohmic contact is made near the front stage amplifier circuit 2, the impedance of the first earth electrode 9 and the parasitic current of the output stage amplifier circuit 1 which sucks a large current will cause a considerable A large potential drop occurs, which destabilizes the potential of the semiconductor chip 6 near the front stage amplifier circuit 2, making it easy to cause oscillations and the like. On the other hand, according to the present invention, since the parasitic current near the front stage amplifier circuit 2 is extremely small compared to the parasitic current near the output stage amplifier circuit 1, the potential and drop of the third earth electrode 11 itself are extremely small. very few,
In addition, since the air from the first earth pad 7 onwards is drawn out by the low impedance thin metal wire and the external lead, it is not affected by the parasitic current sucked out by the first ground electrode 9, It is possible to stabilize the potential of the semiconductor chip 6 and prevent circuit oscillation and generation of parasitic thyristors. Further, since it is independent from the semiconductor chip 6 near the output stage amplifier circuit 1, it is not affected by the parasitic current of the output stage amplifier circuit 1, which handles a large current. Incidentally, if the current handled by the output stage amplifier circuit 1 is quite large and the impedance of the thin metal wire becomes a problem, a method of providing an independent ground pad exclusively for the third earth electrode 11 may also be considered.
Furthermore, by arranging the third ground electrode 11 approximately in the center of the first and second channel regions so as to be symmetrical with respect to the upper and lower lines, the potential of the semiconductor chip 6 in each channel becomes unbalanced. is prevented. This means that the first and second earth electrodes 9, 1
The same applies to 0, so the first and second ground pads 7 and 8 are connected to the first and second ground electrodes 9 and 1.
0 is placed in the center of these lines so that they are symmetrical.

(g) Effects of the Invention As explained above, according to the present invention, the parasitic current of the semiconductor chip 6 in the region where the front-stage amplifier circuit 2 is formed can be effectively sucked out by the third earth electrode 11. Therefore, there is an advantage that the potential of the semiconductor chip 6 in the region of the preamplifier circuit 2 can be stabilized, thereby preventing circuit oscillation and generation of parasitic thyristors. Furthermore, by connecting the third earth electrode 11 directly to the first earth pad 7,
It also has the advantage of being able to completely eliminate the influence on other circuits when sucking out the parasitic current of the preamplifier circuit 2.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a semiconductor integrated circuit device of the present invention, FIG. 2 is a circuit diagram showing a general amplifier circuit,
FIG. 3 is a plan view showing a conventional semiconductor integrated circuit device. 1 is a large signal system output stage amplifier circuit, 2 is a small signal system front stage amplifier circuit, 6 is a semiconductor chip, 7 and 8 are first and second earth pads, and 9 to 11 are first to third earth electrodes. It is.

Claims (1)

[Claims] 1. A ground potential is applied to the output stage amplifier circuit, the front stage amplifier circuit provided in front of the output stage amplifier circuit, a first ground electrode that is in ohmic contact with the semiconductor chip so as to surround the power transistor of the output stage amplifier circuit, and the front stage amplifier circuit. A semiconductor integrated circuit device comprising a second earth electrode for applying voltage, a first earth pad for external connection connected to the first earth electrode, and a second earth pad for external connection connected to the second earth electrode, A semiconductor integrated circuit characterized in that a third ground electrode is provided which is in ohmic contact with the semiconductor chip only in the region where the pre-stage amplifier circuit is formed, extends over the semiconductor chip, and is connected to the first ground pad. circuit device.