JP2001094362A - Transmission amplifier - Google Patents

Abstract

(57) Abstract: A high output is obtained by a transmission amplifier built in a semiconductor integrated circuit. SOLUTION: The bases of transistors constituting a current mirror pair are connected to each other from a second external connection terminal 7 and a third external connection terminal 8 via an inductor 9, and an emitter is grounded by a first external connection terminal. , The base of the first transistor 2 and the first external connection terminal 6 are connected via the capacitor 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission amplifier used for amplifying a transmission signal of a communication device or the like, and in particular, a transistor for transmission and a bias circuit is built in a semiconductor integrated circuit having a plurality of functional blocks. The present invention relates to a transmission amplifier having a configuration.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram of a conventional transmission amplifier. A conventional transmission amplifier will be described with reference to FIG.
5, 1 is a semiconductor integrated circuit, 2 is a first transistor, 3 is a second transistor, 4 is a constant current source, 5 is a capacitor, 6 is a first external connection terminal, 10 is a high frequency signal source, 11 Is an inductance component of the package, 13 is an output terminal, and 15 is a resistor.

[0005] The semiconductor integrated circuit 1 includes first and second transistors 2 and 3, a constant current source 4, a capacitor 5, a resistor 15, and a high-frequency signal source 10. Here, the semiconductor integrated circuit is obtained by forming each circuit element on a silicon substrate. The constant current source 4 is the first transistor 2
The collector and the base are connected. The base of the first transistor 2 and the base of the second transistor 3 are connected via a resistor 15. Also, the first and second transistors 2,
The first and second transistors 2 and 3 form a current mirror pair by connecting both of the emitters 3 to the first external connection terminal 6.

[0004] The base of the first transistor 2 is connected to the emitter via a capacitor 5. The first external connection terminal 6 is connected to a ground outside the semiconductor integrated circuit 1. Here, the semiconductor integrated circuit 1 is housed in a package, and connection to the ground is made via wires and leads of the package. Therefore, the inductance component 11 of the package exists as the inductance caused by the wires and the leads.

[0005] The collector of the second transistor 3 is connected to the choke coil 12 and the output terminal 13. When a high-frequency signal from the high-frequency signal source 10 is input to the base of the second transistor 3, the amplified signal is output from the output terminal 13.

Here, the resistor 15 and the capacitor 5 function as a low-pass filter to prevent a high-frequency signal from leaking to the first transistor 2 side.

[0007]

However, the transmission amplifier shown in the above-mentioned conventional example has a problem that a sufficient output cannot be obtained because the gain is reduced at the time of high output.

FIG. 2 shows input / output characteristics of the transmission amplifier of FIG. The characteristic plotted by a broken line in FIG. 2 indicates the input / output characteristic of the conventional example. From FIG. 2, the gain at the time of inputting a small signal (input -30 dBm) is 10 dB, but the gain decreases as the input power increases. When a large signal is input (input 0 dBm), the gain is reduced to 3 dB, and the output is only 3 dBm.

The cause of the decrease in gain is that the resistor 15 is used in a low-pass filter for cutting a high-frequency signal in FIG. As the input power increases, the base current increases, the collector current increases, and the output power increases. Here, the voltage drop across the resistor 15 increases with an increase in the base current, so that the base bias potential of the second transistor 3 decreases, which acts to suppress the collector current.

On the other hand, as a method of suppressing a decrease in gain at the time of high output, there is a method of setting a large initial current. As an adverse effect of this method, since a large collector current flows even when a small signal is input, the operation efficiency at the time of a small signal is significantly reduced. Also, the transistor amplification factor hf
Since characteristics change due to variations in e and the like, it is difficult to obtain stable characteristics, particularly when a transmission amplifier is built in a semiconductor integrated circuit, and the yield decreases. In addition, the temperature characteristics tend to deteriorate.

Another problem of the conventional transmission amplifier is that high-frequency signals leak to other functional circuit blocks in the integrated circuit. In FIG. 5, the emitters of the first and second transistors 2 and 3 are connected to ground via a common first external connection terminal 6. Here, since the inductance component 11 of the package has a common impedance, a part of the voltage of the large high-frequency signal flowing through the first transistor 2 operating as an amplifier circuit is excited by the inductance component 11 of the package. This voltage is transmitted to the first transistor 2 operating as a bias circuit. This causes a problem that the bias voltage fluctuates. This voltage is supplied to the constant current source 4 through the first transistor.
Will leak out. Then, the high-frequency signal leaks from the constant current source 4 to other functional circuit blocks connected by a current mirror or the like, causing so-called isolation degradation.
For example, leakage to the high-frequency signal source 10 shown in FIG. 5 may cause deterioration of noise characteristics or oscillation due to feedback. Such a phenomenon becomes a problem particularly in an integrated circuit in which communication functions are integrated.

[0012]

According to the present invention, both bases of a first and a second transistor constituting a current mirror pair built in a semiconductor integrated circuit are connected via inductors from second and third external connection terminals. And the emitters of the first and second transistors are grounded from a first external connection terminal, and the base of the first transistor and the emitter of the first transistor are connected via a capacitor, thereby providing high output. Even when the base current increases sometimes, the base amplifier does not change in the base bias potential, thereby realizing a transmission amplifier capable of obtaining a high output. Further, the present invention realizes enhancement of isolation to other functional circuit blocks in the semiconductor integrated circuit.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first transistor forming a parent side of a current mirror pair built in a semiconductor integrated circuit,
A second transistor forming a child side of the current mirror pair, a constant current source and a capacitor built in the semiconductor integrated circuit, and first, second and third external connections provided in the semiconductor integrated circuit A constant current source connected to a collector of the first transistor, a collector connected to a base of the first transistor, and emitters of the first and second transistors connected to the first transistor. Connected to ground or a power supply via an external connection terminal of the first transistor, the base of the first transistor and the emitter of the first transistor are connected via the capacitor, and the bases of the first and second transistors are respectively connected. Connected to the second and third external connection terminals, and connected to the second and third external connection terminals via the inductance. And is intended for amplifying by inputting a high frequency signal to the base of said second transistor. Since the base bias potential does not decrease even at the time of high output, the gain does not decrease and high output can be obtained.

Further, a first transistor forming a parent side of a current mirror pair built in the semiconductor integrated circuit, a second transistor forming a child side of the current mirror pair, and a second transistor forming a parent side of the current mirror pair are built in the semiconductor integrated circuit. A constant current source and a capacitor, and first and second capacitors provided in the semiconductor integrated circuit.
A second transistor connected to the collector of the first transistor; a collector connected to the base of the first transistor; a first transistor connected to a base of the first transistor; The emitter of the second transistor is connected to ground or a power supply via the first external connection terminal; the emitter of the second transistor is connected to the ground or power supply via the fourth external connection terminal; Connecting the base of the transistor and the emitter of the first transistor via the capacitor;
Connecting the bases of the first and second transistors to the second and third external connection terminals, respectively;
And a third external connection terminal connected via the inductance, and amplification is performed by inputting a high-frequency signal to the base of the second transistor. And, the ground terminal of the emitter of the first transistor and the second terminal
Since the ground terminal of the emitter of the transistor is independently provided, high-frequency signals can be prevented from leaking to the bias circuit side including the first transistor, and stable characteristics can be obtained. Then, it is possible to prevent a high-frequency signal from leaking to another functional circuit block in the semiconductor integrated circuit.

Further, a first transistor forming a parent side of a current mirror pair built in the semiconductor integrated circuit, a second transistor forming a child side of the current mirror pair, and a second transistor forming a parent side of the current mirror pair are built in the semiconductor integrated circuit. A constant current source, first, second, third, and fourth external connection terminals provided on the semiconductor integrated circuit; an inductance; and a capacitor, wherein the constant current source is a collector of the first transistor. , The collector and the base of the first transistor are connected, the emitter of the first transistor is connected to the ground or a power supply via the first external connection terminal, and the emitter of the second transistor is connected to the ground. The fourth
Connected to ground or power through the external connection terminal of
Connecting the bases of the first and second transistors to the second and third external connection terminals, respectively;
And connecting a third external connection terminal via the inductance, connecting the second external connection terminal to ground or a power supply via the capacitor, and inputting a high-frequency signal to a base of the second transistor. Amplification is performed by Since the amplifier circuit including the second transistor and the bias circuit including the first transistor are completely independent of each other in terms of alternating current, a high-frequency signal does not leak to the constant current source, and other functions in the semiconductor integrated circuit can be performed. Leakage of a high-frequency signal into the circuit block can be suppressed more reliably.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a circuit diagram showing a configuration of a transmission amplifier according to Embodiment 1 of the present invention.

The transmission amplifier according to the present embodiment will be described with reference to FIG. In FIG. 1, 1 is a semiconductor integrated circuit, 2 is a first transistor, 3 is a second transistor, 4 is a constant current source, 5 is a capacitor, 6 is a first external connection terminal, 7
Is a second external connection terminal, 8 is a third external connection terminal, 9 is an inductor, 10 is a high frequency signal source, 11 is an inductance component of the package, 12 is a choke coil, and 13 is an output terminal.

The semiconductor integrated circuit 1 includes first and second transistors 2 and 3, a constant current source 4, a capacitor 5, and a high frequency signal source 10. Here, the semiconductor integrated circuit is obtained by forming each circuit element on a silicon substrate. The constant current source 4 is connected to the collector of the first transistor 2, and the collector and the base are connected. The base of the first transistor 2 and the base of the second transistor 3 are connected to a second external connection terminal 7 and a third external connection terminal 8, respectively.
The third external connection terminals 7 and 8 are connected to each other via an inductor 9. The emitters of the first and second transistors 2 and 3 are both connected to the first external connection terminal 6.
, The first and second transistors constitute a current mirror pair. The base of the first transistor 2 is connected to the emitter via the capacitor 5.

The first external connection terminal 6 is connected to the ground. Here, the semiconductor integrated circuit 1 is housed in a package, and connection to the ground is made via wires and leads of the package. Therefore, the inductance component 11 of the package exists as the inductance caused by the wires and leads. The collector of the second transistor 3 is connected to the choke coil 12 and the output terminal 13.

The high frequency signal from the high frequency signal source 10
Is input to the base of the transistor 3, the amplified signal is output from the output terminal 13.

Here, the inductor 9 and the capacitor 5 function as a low-pass filter to prevent a high-frequency signal from being input to the first transistor 2 side.

FIG. 2 shows input / output characteristics of the transmission amplifier of FIG. In FIG. 2, the characteristics plotted by solid lines indicate the input / output characteristics of the present embodiment. As can be seen from FIG. 2, the gain does not decrease even when the input power increases, and when a large signal is input (input 0
dBm), the gain is 10 dB, and the output is 10 dBm.
Has been obtained. Since the inductor 9 is used for connection between the bases as described above, even when the base current of the second transistor 3 increases at the time of high output, the base bias potential does not decrease, and a high-output transmission amplifier can be realized. .

When the signal from the high-frequency signal source 10 is small, the base current is also small, so that good operation efficiency can be obtained even when a small signal is output. Further, compared with the case where a resistor is used for the connection between the bases, it is less affected by the variation of the current amplification factor hfe, and the temperature characteristic is improved.

(Embodiment 2) FIG. 3 is a circuit diagram showing a configuration of a transmission amplifier according to Embodiment 2 of the present invention. In FIG. 3, reference numeral 14 denotes a fourth external connection terminal. The same components as those in FIG. 1 are denoted by the same reference numerals.

The difference between this embodiment and the first embodiment is that the emitters of the first and second transistors 2 and 3 are grounded independently. That is, the first transistor 2
Are connected from the first external connection terminal 6 to the ground. On the other hand, the emitter of the second transistor 3 is connected to the ground from the fourth external connection terminal 14. Here, the base of the first transistor 2 is connected to the emitter of the first transistor 2 via the capacitor 5. This is the feature. Here, if the base of the first transistor 2 is connected to the fourth external connection terminal 14 via the capacitor 5 and grounded, sufficient characteristics cannot be obtained. In the case of this configuration, since a high-frequency signal is applied between the base and the emitter of the first transistor 2 at the time of high output, rectification is performed by the first transistor 2 and the base bias potential is rapidly lowered.

In this embodiment, since the ground terminal of each emitter is independent, the high frequency signal of the amplifier circuit including the second transistor 3 is hardly leaked to the bias circuit including the first transistor 2. I have.

That is, since the emitter of the second transistor 3 is grounded via the fourth external connection terminal 14, the emitter of the second transistor 3 is connected to the first transistor 2 which is grounded via the first external connection terminal 6. Of the high-frequency signal becomes small. Therefore, the influence on the bias potential fluctuation can be reduced, and the deterioration of isolation from other functional circuit blocks through the constant current source 4 can be suppressed.

(Embodiment 3) FIG. 4 is a circuit diagram showing a configuration of a transmission amplifier according to Embodiment 3 of the present invention. 4, the same components as those in FIGS. 1 and 3 are denoted by the same reference numerals.

The difference between this embodiment and the second embodiment is that the capacitor 5 is provided outside the semiconductor integrated circuit 1. That is, a connection point between the inductor 9 and the second external connection terminal 7 is connected to the ground via the capacitor 5.

The feature of this embodiment is that the first transistor 2
And the amplifier circuit including the second transistor 3 are completely separated from each other in terms of AC.
The inductance components 11 of the package are the first,
Second, third and fourth external connection terminals 6, 7, 8, 14
However, in the present configuration, the capacitor is not affected by the inductance component and is completely separated by the grounding of the capacitor 5.

Here, it is difficult for the capacitor built in the semiconductor integrated circuit 1 to secure a capacity sufficient to short-circuit sufficiently in the AC, and the inductance component 11 of the package
Causes degradation of isolation.

Although the isolation can be improved by the configuration of the second embodiment, even greater isolation can be obtained with this configuration. Then, leakage of the high-frequency signal to other functional circuit blocks can be suppressed.

The same effect can be obtained by using a diode instead of the first transistor. Although the high-frequency signal source is built in, it may be configured outside the semiconductor integrated circuit.

[0035]

As apparent from the above description, the following effects can be obtained according to the oscillator of the present invention.

A first transistor forming a parent side of a current mirror pair incorporated in the semiconductor integrated circuit, a second transistor forming a child side of the current mirror pair,
A constant current source and a capacitor built in the semiconductor integrated circuit; first, second, and third external connection terminals provided in the semiconductor integrated circuit; and an inductance. Connecting the collector of the first transistor to the base of the first transistor, connecting the emitters of the first and second transistors to ground or a power supply via the first external connection terminal, Connecting the base of one transistor to the emitter of the first transistor via the capacitor; connecting the bases of the first and second transistors to the second and third external connection terminals, respectively; Since the second and third external connection terminals are connected via the inductance, the base bias potential is reduced even at high output. There is no Rukoto, it is possible to realize a high output transmission amplifier.

Further, a first transistor forming a parent side of a current mirror pair built in the semiconductor integrated circuit, a second transistor forming a child side of the current mirror pair, and a second transistor forming a parent side of the current mirror pair are built in the semiconductor integrated circuit. A constant current source, first, second, third, and fourth external connection terminals provided on the semiconductor integrated circuit; an inductance; and a capacitor, wherein the constant current source is a collector of the first transistor. , The collector and the base of the first transistor are connected, the emitter of the first transistor is connected to the ground or a power supply via the first external connection terminal, and the emitter of the second transistor is connected to the ground. The fourth
Connected to ground or power through the external connection terminal of
Connecting the bases of the first and second transistors to the second and third external connection terminals, respectively;
And the third external connection terminal is connected via the inductance, and the second external connection terminal is connected to the ground or the power supply via the capacitor.
Leakage of high-frequency signals to other functional circuit blocks can be suppressed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a transmission amplifier according to a first embodiment of the present invention.

FIG. 2 is an input / output characteristic diagram of the transmission amplifier.

FIG. 3 is a circuit diagram of a transmission amplifier according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a transmission amplifier according to a third embodiment of the present invention.

FIG. 5 is a circuit diagram of a conventional transmission amplifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor integrated circuit 2 1st transistor 3 2nd transistor 4 Constant current source 5 Capacitor 6 1st external connection terminal 7 2nd external connection terminal 8 3rd external connection terminal 9 Inductor 10 High frequency signal source 11 Package Inductance component 14 Fourth external connection terminal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J091 AA01 AA41 CA35 CA51 FA20 HA02 HA25 HA29 HA33 KA05 KA09 KA12 MA21 SA14 TA02 UW08 5J092 AA01 AA41 CA35 CA51 FA20 HA02 HA25 HA29 HA33 KA05 KA09 KA12 MA21 SA14 TA02

Claims (3)

[Claims] A first transistor forming a parent side of a current mirror pair incorporated in a semiconductor integrated circuit; a second transistor forming a child side of the current mirror pair;
A constant current source and a capacitor built in the semiconductor integrated circuit; first, second, and third external connection terminals provided in the semiconductor integrated circuit; and an inductance. Connecting the collector of the first transistor to the base of the first transistor, connecting the emitters of the first and second transistors to ground or a power supply via the first external connection terminal, Connecting the base of one transistor to the emitter of the first transistor via the capacitor; connecting the bases of the first and second transistors to the second and third external connection terminals, respectively; Second and third external connection terminals are connected via the inductance, and a high-frequency signal is input to the base of the second transistor. Transmission amplifier for amplifying the said. 2. A first transistor forming a parent side of a current mirror pair incorporated in a semiconductor integrated circuit, a second transistor forming a child side of the current mirror pair,
A constant current source and a capacitor built in the semiconductor integrated circuit; and first, second, and
Third and fourth external connection terminals, an inductance, the constant current source connected to a collector of the first transistor, a collector connected to a base of the first transistor, An emitter connected to ground or a power supply via the first external connection terminal; an emitter connected to the ground or a power supply via the fourth external connection terminal; A base connected to the emitter of the first transistor through the capacitor;
And the base of the second transistor
And a third external connection terminal, a transmission amplifier for connecting the second and third external connection terminals via the inductance, and performing amplification by inputting a high-frequency signal to the base of the second transistor. . 3. A first transistor forming a parent side of a current mirror pair incorporated in a semiconductor integrated circuit, a second transistor forming a child side of the current mirror pair,
A constant current source built in the semiconductor integrated circuit; first, second, third and fourth external connection terminals provided in the semiconductor integrated circuit; an inductance; and a capacitor. Connecting the collector of the first transistor, connecting the collector and base of the first transistor, connecting the emitter of the first transistor to ground or a power supply via the first external connection terminal, Connecting the emitter of the second transistor to ground or a power supply via the fourth external connection terminal, connecting the bases of the first and second transistors to the second and third external connection terminals, respectively; The second and third external connection terminals are connected via the inductance, and the second external connection terminal is connected to ground or power via the capacitor. Transmission amplifier for amplifying the connected inputs a high-frequency signal to the base of said second transistor things.