JP3006981B2 - Amplifier circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC signal amplifying circuit whose gain can be adjusted only by wire bonding.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 7, there is an amplifier circuit which can adjust a gain by adding a resistor outside the integrated circuit. In FIG. 7, a differential amplifier A101 has two input terminals a and b and one output terminal c.
It has a gain adjustment terminal P101. FIG. 8 is a specific circuit diagram of the amplifier circuit. Hereinafter, the operation of the amplifier circuit will be briefly described with reference to FIG.

The voltage difference between the input terminals a and b is converted into a change current i by transistors Q101 and Q102, and is converted into a voltage again by an external resistor R101 connected to the gain adjustment terminal P101.

[0004] Thus, the output voltage v _c output from the output terminal c _{is, v c = i × R101 ...} (1) becomes, it is understood that it is possible to gain adjustment by an external resistor R101.

[0005]

However, the conventional gain-adjustable amplifier requires an external resistor R101 to adjust the gain. Therefore, a gain adjustment terminal P101 for adding the external resistor R101 and a space are required. Further, there is a problem that the cost of the external resistor R101 is increased.

Particularly, an element having a small number of terminals, for example, a power supply,
In the case of an amplifier circuit provided in a small element having only three terminals of GND and output, there is a problem that the gain cannot be adjusted by the external resistor R101.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an amplifier circuit that does not require an external resistor and that can adjust the gain without increasing the number of terminals or space.

[0008]

In order to achieve the above object, an invention according to claim 1 is an amplifier formed by monolithic integrated circuit technology and formed by cascading two or more differential amplifiers by AC coupling. In the circuit, a pad is connected to one of two output terminals for sending an output signal to the next-stage differential amplifier in each of the differential amplifiers, and a frame or a frame having the same potential as a power supply or a ground terminal is connected. The gain is adjusted by wire bonding the pad to the substrate pattern. According to a second aspect of the present invention, there is provided an amplifier circuit formed by monolithic integrated circuit technology and cascaded by two or more differential amplifiers by AC coupling. A pad is connected to one of two input terminals in an output circuit for generating an output signal to be supplied to two output terminals of the differential amplifier, and the above-mentioned is connected to a frame or substrate pattern having the same potential as a power supply or a ground terminal The gain is adjusted by wire bonding the pad.

According to a third aspect of the present invention, in the amplifier circuit according to the first or second aspect, an output signal is provided in the differential amplifier and supplied to the two output terminals. The output circuit is characterized by being constituted by an emitter follower circuit using an NPN transistor.

According to a fourth aspect of the present invention, in the amplifier circuit of the first or second aspect of the present invention, an output signal is provided in the differential amplifier and supplied to the two output terminals. The output circuit is characterized by being constituted by an emitter follower circuit using a PNP transistor.

According to a fifth aspect of the present invention, in the amplifier circuit according to any one of the first to fourth aspects, the number of differential amplifiers cascaded by the AC coupling is n. And the differential amplifier provided with the pad is a first to (n−1) -th differential amplifier,
Each of the (n-1) differential amplifiers is provided with (n-
1) The gain is reduced to (１) ^M times by performing the wire bonding on M pads of the 1 pads.

According to a sixth aspect of the present invention, in the amplifying circuit according to any one of the first to third aspects, an insulating film is used for an AC coupling for cascading the differential amplifiers. A capacitor is used, and the pad is formed on the insulating film capacitor by opening an insulating film window in a metal portion forming an electrode connected to the output terminal in the insulating film capacitor.

According to a seventh aspect of the present invention, in the amplifier circuit according to any one of the second to fifth aspects, an insulation is provided between two input terminals of the output circuit in the differential amplifier. A frequency band limiting capacitor or a phase compensating capacitor composed of a film capacitor is provided, and the pad is provided with an insulating film window by opening an insulating film window in a metal portion forming one of the electrodes in the insulating film capacitor. It is characterized by being formed above.

[0014]

According to the first aspect of the present invention, the pad connected to one of the two output terminals in each of the differential amplifiers of the two or more differential amplifier rows cascaded by AC coupling is connected to the power supply or the ground. By wire bonding to a frame or substrate pattern having the same potential as the terminal, the gain of the amplifier circuit formed by the cascaded differential amplifiers is adjusted.

According to the second aspect of the present invention, a connection is made to one of two input terminals of an output circuit in each differential amplifier of two or more differential amplifier rows cascaded by AC coupling. The resulting pad is wire-bonded to a frame or substrate pattern at the same potential as the power supply or ground terminal, so that the gain of the amplifier circuit formed by the cascaded differential amplifiers is adjusted.

Further, in the invention according to claim 3, the output circuit in the differential amplifier for supplying an output signal to the two output terminals is constituted by an emitter follower circuit using an NPN transistor. Therefore, even if the pad is short-circuited to a frame or substrate pattern having the same potential as the power supply by wire bonding, the PN junction of the NPN transistor is merely biased in the reverse direction, and does not affect the circuit operation. .

Also in the invention according to claim 4, even if the pad is short-circuited to a frame or substrate pattern having the same potential as the ground terminal by wire bonding, the PN junction of the PNP transistor is biased in the reverse direction. It does not affect the circuit operation.

In the invention according to claim 5, among the n differential amplifiers cascaded by the AC coupling, the differential amplifiers provided with the pads are the first to the second stages.
The (n-1) -th stage differential amplifier, and M pads of the (n-1) pads provided in each of the (n-1) differential amplifiers are as described above. And the gain of the amplifier circuit is reduced to (１) ^M times.

Further, in the invention according to claim 6, the pad is insulated from a metal portion forming an electrode connected to the output terminal in an insulating film capacitor used for AC coupling of the differential amplifier. It is formed by opening the membrane window. Thus, the pad formed on the insulating film capacitor is wire-bonded without providing a special area, and the gain of the amplifier circuit is adjusted.

Further, in the invention according to claim 7, the pad is one of a frequency band limiting capacitor provided between the two input terminals of the output circuit and an insulating film capacitor used as a phase compensating capacitor. It is formed by opening an insulating film window in a metal part forming an electrode. Thus, the pad formed on the insulating film capacitor is wire-bonded without providing a special area, and the gain of the amplifier circuit is adjusted.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 is an equivalent circuit diagram of the amplifier circuit of this embodiment.

The amplifying circuit comprises two differential amplifiers 1, 2
Are cascaded by AC coupling via capacitors C1 and C2. Here, A1 and A2 are gains of the differential amplifiers 1 and 2, a and b are input terminals of the differential amplifier 1, and c and d are output terminals of the differential amplifier 1.

In the above configuration, the potential difference between the input terminals a and b is amplified by A1 times with the gain A1, and the voltage is output as the potential difference between the output terminals c and d. That is, Vc−Vd = (Va−Vb) × A1 (2) Here, it is assumed that Vc and Vd have opposite phases, and for the sake of simplicity, the voltage change amounts of Vc and Vd are assumed to be equal. Then, equation (2) can be expressed as follows: 2 × Vc = (Va−Vb) × A1 (3) Vc = (Va−Vb) × A1 / 2 (4)

The output signals from the output terminals c and d are input to the next-stage differential amplifier 2 which is AC-coupled by the capacitors C1 and C2. Then, A2
The output voltage v2 is obtained by multiplication.

However, in this embodiment, the capacitances C1, C2
Is sufficiently large, and the voltages Vc and Vd of the output terminals c and d are all transmitted to the differential amplifier 2 without attenuation. Therefore, the output voltage v2 is given by: v2 = (Vc−Vd) × A2 = (Va−Vb) × A1 × A2 (5) in consideration of the equation (2).

Here, when the pad P1 connected to the output terminal d is short-circuited to the power supply potential or the GND potential so that the output terminal d does not operate, the terminal voltage Vd of the equation (5) becomes "0". Therefore, from equation (5), v2 = Vc × A2 (6). By substituting the equation (4) into the obtained equation (6), v2 = (Va−Vb) × A1 × A2 / 2 (7) As a result, the gain can be reduced to “１”. .

However, the amplifier circuit needs to have an output circuit that does not affect the circuit operation even if the pad P1 is short-circuited to the power supply potential or the GND potential. Therefore, the output circuit described above will be described below.

FIGS. 2 and 3 are specific circuit examples inside the broken line in FIG.

FIG. 2 shows an embodiment in which an emitter follower circuit of an NPN transistor whose emitter terminal is biased with a constant current is used for the output circuit. In the case of the present embodiment is of shorting the pad P1 connected to the emitter of NPN transistor Q4 to the frame or board pattern of the power supply V _CC and the same potential by wire bonding or the like.

In that case, the NPN transistor Q
Since the emitter terminal of No. 4 is short-circuited with the collector terminal, the collector potential becomes higher than the base potential.
As a result, the output terminal d does not operate because the PN junction is biased in the reverse direction, and the circuit operation of the amplifier circuit is hardly affected.

In this embodiment, a pad P1 'is provided at the base of the NPN transistor Q4 (that is, one input terminal of the output circuit), and the pad P1' is set to the same potential as the power supply _Vcc. Almost the same effects can be obtained by short-circuiting.

FIG. 3 shows an embodiment in which an emitter follower circuit of a PNP transistor whose emitter terminal is biased with a constant current is used for the output circuit. In the case of this embodiment, the pad P1 connected to the emitter of the PNP transistor Q8 is short-circuited to the same potential as the GND terminal.

In that case, the PNP transistor Q
Since the emitter terminal 8 is short-circuited to the collector terminal, the emitter potential becomes lower than the base potential.
As a result, as in the case of the above-described embodiment, the output terminal d does not operate because the PN junction is biased in the reverse direction, and the circuit operation of the amplifier circuit is hardly affected.

In this embodiment, a pad P1 'is provided at the base of the PNP transistor Q8 (that is, one input terminal in the output circuit), and the pad P1' is short-circuited to the same potential as the GND terminal. Almost the same effect can be obtained by doing so.

FIG. 4 shows an embodiment of an amplifier circuit in which n differential amplifiers are cascaded in the circuit configuration shown in FIG. (N-1) differential amplifiers 1, from a first stage differential amplifier 1 to a (n-1) th stage differential amplifier (not shown),
One of the output terminals of each of the pads 2, 3,.
By providing P (n-1), the gain can be adjusted by short-circuiting each of the pads P1,..., P (n-1) to the power supply potential or the GND potential.

As described above, the (n-1) pads P
One of the 1,..., P (n-1) is short-circuited to the power supply potential or the GND potential so that the one output terminal does not operate, thereby reducing the gain of the amplifier circuit to 1/2. be able to. Therefore, when the M pads are short-circuited to the power supply potential or the GND potential, and the gain of the amplifier circuit is G, G = A1 × A2 ×... An × (1/2) ^M (8) However, M ≦ (n−1).

In the embodiment shown in FIG. 2 or FIG. 3, when the capacitance of the insulating film of the integrated circuit is used as the capacitances C1 and C2 used for the AC coupling, one electrode of the capacitance C2 is connected. By providing the pad P1 connected to the connected output terminal d on the capacitor C2, the area required for the pad in the integrated circuit can be saved.

[0039] Similarly, in the case where in the embodiment shown in FIG. 2 or 3, using the insulating film capacitance of the integrated circuit as a capacitance C _f using the frequency band limitation, capacitance C
NPN transistor Q4 connected to one electrode of _f
Base by providing on the (one input terminal of the output circuit) pad P1 'capacity C _f that are connected to, it is possible to save the area of the integrated circuits required for the pad. This is true even when the capacitance of the insulating film of the integrated circuit is used as the capacitance used for the phase compensation.

FIG. 5 is a pattern example of a nitride film capacitance, which is one of the insulating film capacitances in the integrated circuit, and FIG. 6 is a cross-sectional view taken along the line XX 'in FIG. In the nitride film capacitor having a structure as shown in FIGS. 5 and 6, an insulating film window 12 is opened in a metal portion of one electrode 10 of the nitride film capacitor to form a pad P (in this embodiment, pad P1 or pad P1). '). Thus, the pad P is formed on the nitride film capacitor.
Is formed, it is possible to configure an amplifier circuit having the above-described effects without securing an area for the pad P in the integrated circuit.

The specific circuit diagrams for realizing the above embodiments are not limited to the circuit diagrams shown in FIGS.

[0042]

As is apparent from the above description, the amplifier circuit according to the first aspect of the present invention includes any one of two output terminals of each of two or more differential amplifiers cascaded by AC coupling. The gain can be adjusted by connecting a pad to one of the pads and wire-bonding the pad to a frame or substrate pattern having the same potential as the power supply or ground terminal, so that the gain can be adjusted without an external resistor.

Therefore, the gain can be adjusted without providing the terminal for the external resistor or providing a space for the external resistor. As a result, the gain can be easily adjusted even for an amplifier circuit for an element having a small number of terminals to which an external resistor cannot be attached.

Further, the amplifier circuit according to the second aspect of the present invention comprises:
A pad is connected to one of two input terminals of an output circuit in each differential amplifier of two or more differential amplifiers cascaded by AC coupling, and a frame or a frame having the same potential as a power supply or a ground terminal is connected. Since the gain can be adjusted by wire bonding the pad to the substrate pattern, the gain can be adjusted without an external resistor.

Therefore, the gain can be adjusted without providing the terminal for the external resistor or providing a space for the external resistor.

Further, the amplifier circuit according to the third aspect of the present invention comprises:
Since the output circuit in the differential amplifier is constituted by an emitter follower circuit using an NPN transistor, even if the pad is short-circuited by wire bonding as described above, only the PN junction of the NPN transistor is biased in the reverse direction. Therefore, the operation of the circuit is not affected.

The amplifier circuit of the invention according to claim 4 is:
Similarly to the case of the amplifier circuit according to the third aspect of the present invention, even if the pad is short-circuited by wire bonding as described above, only the PN junction of the PNP transistor constituting the output circuit is biased in the reverse direction. There is no effect on the circuit operation.

Further, the amplifier circuit of the invention according to claim 5 comprises:
The number of the differential amplifiers connected in cascade by the AC coupling is n, and the differential amplifiers provided with the pads are the first to (n−1) -th differential amplifiers.
Since the M pads of the (n-1) pads provided in each of the (n-1) differential amplifiers are wire-bonded, the gain is reduced to (1/2) ^M times. can do.

The amplifier circuit of the invention according to claim 6 is:
An insulating film capacitor is used for the AC coupling for cascade-connecting the differential amplifier, and the pad is formed by opening an insulating film window in a metal portion forming an electrode connected to the output terminal in the insulating film capacitance. Since it is formed on the insulating film capacitor, the area for forming the pad in the integrated circuit can be saved.

The amplifier circuit of the invention according to claim 7 is:
Between the two input terminals of the output circuit in the differential amplifier, a frequency band limiting capacitor or a phase compensating capacitor composed of an insulating film capacitor is provided, and the pad is any one of the insulating film capacitors. Since an insulating film window is opened in a metal part where an electrode is formed, the insulating film is formed on the insulating film capacitor, so that the area for forming the pad in the integrated circuit can be saved.

[Brief description of the drawings]

FIG. 1 is an equivalent circuit diagram of an amplifier circuit according to the present invention.

FIG. 2 is a specific circuit diagram inside a broken line in FIG.

FIG. 3 is a specific circuit diagram different from FIG. 2 inside a broken line in FIG. 1;

FIG. 4 is an equivalent circuit diagram different from FIG.

FIG. 5 is a diagram showing a pattern of a nitride film capacitance.

FIG. 6 is a sectional view taken along the line XX ′ in FIG. 5;

FIG. 7 is an equivalent circuit diagram of an amplifier circuit whose gain can be adjusted by an external resistor.

8 is a specific circuit diagram of the amplifier circuit shown in FIG.

[Explanation of symbols]

1-4: Differential amplifier, 10, 11: Capacitance electrode, 12: Insulating film window, a, b: Input terminal, c, d: Output terminal, C1, C2
... Capacity, P1 ~ P (n-1), P1 '... Pad, A1 ~ An
... Gain, Q1 ~ Q4 ... NPN transistor, Q5 ~
Q8: PNP transistor.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-61-53809 (JP, A) JP-A-52-30364 (JP, A) JP-A-58-108810 (JP, A) JP-A-58-108 197905 (JP, A) JP-A-58-197906 (JP, A) JP-A-54-90954 (JP, A) JP-A-57-36016 (JP, U) (58) Fields investigated (Int. ⁷ , DB name) H03G 1/00-3/18

Claims (7)

(57) [Claims] 1. An amplifier circuit formed by monolithic integrated circuit technology and formed by cascade-connecting two or more differential amplifiers by AC coupling, wherein an output signal is supplied to a next-stage differential amplifier in each of the differential amplifiers. The gain is adjusted by connecting a pad to one of the two output terminals for transmission and wire bonding the pad to a frame or substrate pattern having the same potential as the power supply or ground terminal. Amplifier circuit. 2. An amplifier circuit formed by monolithic integrated circuit technology and formed by cascading two or more differential amplifiers by AC coupling. A pad is connected to one of two input terminals in an output circuit for generating an output signal to be supplied to one output terminal, and the pad is wire-bonded to a frame or substrate pattern having the same potential as a power supply or a ground terminal. An amplifier circuit characterized in that the gain is adjusted by changing the gain. 3. The amplifier circuit according to claim 1, wherein the output circuit in the differential amplifier for generating an output signal to be supplied to the two output terminals is an emitter follower using an NPN transistor. An amplifier circuit comprising a circuit. 4. The amplifier circuit according to claim 1, wherein the output circuit in the differential amplifier for generating an output signal to be supplied to the two output terminals is an emitter follower using a PNP transistor. An amplifier circuit comprising a circuit. 5. The amplifier circuit according to claim 1, wherein the number of differential amplifiers cascaded by the AC coupling is n, and the pad is provided. Differential amplifiers are from the first stage
The (n-1) -th differential amplifier is provided in each of the (n-1) differential amplifiers.
1) An amplifier circuit characterized in that the gain is reduced to ( ^M ) ^M times by performing wire bonding on M pads of the pads. 6. The amplifier circuit according to claim 1, wherein an AC coupling for cascading the differential amplifiers uses an insulating film capacitor, and the pad comprises: An amplifier circuit formed on the insulating film capacitor by opening an insulating film window in a metal portion of the insulating film capacitor which forms an electrode connected to the output terminal. 7. An amplifier circuit according to claim 2, wherein a frequency band limitation comprising an insulating film capacitance is provided between two input terminals of said output circuit in said differential amplifier. Wherein the pad is formed on the insulating film capacitor by opening an insulating film window in a metal portion forming one of the electrodes in the insulating film capacitor. Amplifier circuit.