JPH0661763A - High frequency amplifier circuit - Google Patents

Abstract

PURPOSE:To provide a circuit suitable for circuit integration by reducing the circuit scale with respect to the high frequency amplifier circuit used for, e.g. a digital portable telephone set. CONSTITUTION:The high frequency amplifier circuit comprising a 1st bias voltage application section 3a in which a collector of a 2nd transistor(TR) whose emitter connects to a constant current source connects to an emitter and a base of a 3rd TR via a resistor and a capacitor and a DC voltage is fed to a collector of a 3rd TR and comprising a 1st bias voltage application section 3a applying a bias voltage to the 1st high frequency amplifier section is provided with a 2nd high frequency amplifier section 2b, a bias voltage application section 3b and a changeover section 4 interrupting the application of a DC voltage in the DC voltages fed to the 1st and 2nd high frequency amplifier sections, emitters of the 3rd TR are directly connected and a high frequency signal is extracted via a DC block capacitor and a reference voltage is applied in common to 1st and 2nd bias voltage application sections.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency amplifier circuit used in, for example, a digital mobile phone.

Mobile communication devices such as digital mobile phones are
It tends to be smaller and consume less power. For this reason, it is necessary to reduce the circuit scale of the amplifier circuit and make it suitable for IC.

[0003]

2. Description of the Related Art FIG. 6 is a block diagram of a conventional example. Normally, in the high frequency amplifier circuit used for digital mobile phones,
As shown in the figure, the high-frequency amplification part 12 is the antenna ANT ₂
The signal received from is amplified and added to the high frequency switch 13, and the high frequency amplification part 11 amplifies the signal received from the reception-only antenna ANT ₁ and added to the high frequency switch 13. Therefore, the high frequency switch selects the output of either one of the high frequency amplifying portions in accordance with a control signal from the outside and sends it to the outside. In addition, 15 is a transmitter and 14 is a duplexer.

Here, the high frequency switch is, for example, GaAs.
A MMIC (monolithic microwave IC) switch using FET is used, and the amplification part on the non-selected side is electrically separated, so the high-frequency amplification part that was not separated is separated from the high-frequency amplification part. The deterioration of the characteristics is prevented by eliminating the influence of the parts.

[0005]

Here, when considering a high frequency amplifier circuit as an IC, a silicon bipolar transistor is used for the high frequency amplifier part in terms of price and mass productivity, but the high frequency switch is a silicon bipolar transistor. Since it is technically difficult to configure with a transistor, another IC (
For example, two types of ICs are required as GaAs ICs).

Therefore, the above-mentioned high-frequency amplifier circuit using the high-frequency switch is not suitable for use as an IC, and there is a problem that it is difficult to reduce the circuit scale. It is an object of the present invention to reduce the circuit scale and provide a circuit suitable for use in an IC.

[0007]

FIG. 1 is a block diagram showing the principle of the first and second aspects of the present invention. In the figure, 2a indicates that the emitter of the first transistor is grounded by a resistor, the collector is grounded by a capacitor, and is connected to the emitter of a second transistor, and the collector of the second transistor is connected via a resistor and a capacitor. It is connected to the emitter and the base of the third transistor, the direct current voltage is supplied to the collector of the third transistor, the high frequency signal is input to the base of the second transistor, and the emitter of the third transistor is supplied. This is the first high-frequency amplification portion for output.

Reference numeral 3a is a first bias voltage supply portion for generating a predetermined bias voltage using the applied reference voltage and supplying it to the bases of the first to third transistors, and 2b is a first high frequency amplifier. A second high-frequency amplification part having the same configuration and function as the part, 3b has a second bias voltage supply part having the same configuration and function as the first bias voltage supply part, and 4 corresponds to the state of the switching signal to be applied. Of the DC voltage supplied to the first and second high frequency amplifying parts, one of the DC voltages is switched off.

According to the first aspect of the present invention, the emitters of the third transistor in the first and second high frequency amplifying portions are directly connected to each other, the high frequency signal is taken out through the DC blocking capacitor, and the reference voltage is set. The configuration is such that it is applied to both the first and second bias voltage supply portions.

In the second aspect of the present invention, the reference voltage is commonly applied to the first and second bias voltage supply portions via the first and second resistors.

[0011]

According to the first aspect of the present invention, by directly connecting the output terminals of the two high-frequency amplification parts in terms of direct current, one of the high-frequency amplification parts is turned off when the DC voltage (V _CC ) of the other high-frequency amplification part is turned off at the switching part. The DC voltage appearing at the output end of the high frequency amplifying part also appears at the output end of the other high frequency amplifying part, and makes the output impedance of this amplifying part high impedance (described later in detail). Therefore, even if the high frequency switch is not provided, one high frequency amplifying portion is hardly affected by the other high frequency amplifying portion.

Since the output terminal is directly connected, a leakage current of about several hundred μA flows in the high frequency amplification section which is not operating. In the second aspect of the present invention, in order to reduce the leakage current, the reference voltage is applied to both the first and second bias voltage supply portions via a resistor of, for example, several kilohms to several tens of kilohms. As a result, the reference voltage applied to the other high-frequency amplification section drops, so the leakage current drops and the power consumption of this amplification section drops.

That is, it is possible to reduce the circuit scale and provide a circuit suitable for use in an IC.

[0014]

FIG. 2 is a block diagram of the first and second embodiments of the present invention, FIG. 3 is an explanatory diagram of the output impedance of an amplifier, FIG. 4 is a gain characteristic diagram of the amplifier, and FIG. It is a frequency conversion part block diagram used.

Here, the switches SW ₁ and SW ₂ are components of the switching portion. In addition, the same reference numerals denote the same objects throughout the drawings. Below, switches SW ₁ and SW ₂ are in solid line.
As shown in FIG. 3, the resistors R _7a and R _7b are set to 0 (the high frequency amplification part 2a is in the operating state and the high frequency amplification part 2b is in the non-operating state).
The operation of FIG. 2 will be described with reference to FIG. The control signal for driving the switch is applied from the outside.

[0016] First, the bias voltage supply section 3a includes a transistor Q _21a (hereinafter, abbreviated as Q _21a), is intended for supplying a base voltage necessary based Q _22a, Q _23a, 4
1 transistors Q _31a , Q _32a , Q _33a , Q _34a in the vertical direction
Since they are stacked and connected in a row, the voltage drops below the voltage _Vcc each time they pass through the transistor in each stage.

For example, if V _cc = + 5V, V of Q _{34a
Since be} is about 0.8V, the emitter voltage of Q _34a is 4.2V. Then, if the base voltage of Q _33a supplied from the reference voltage generation part 4 is, for example, + 2.8V, the emitter voltage of Q _33a is + 2V, the emitter voltage of Q _32a is + 1.2V, and these voltages are Q _23a. , Q _22a , Q _21a applied to the base. The V _be of Q _{33a and} Q _32a is set to about 0.8V as above.

Now, the Q applied with such a bias voltage
_When a high frequency signal is applied to the base of _22a via the capacitor C ₁₁ , the high frequency signal is applied to the collector of Q _22a and the base of Q _23a via the capacitor C ₅ . So Q _23a
The high-frequency signal further amplified by and then amplified from the emitter is output via the capacitor C ₁₃ and the terminal OUT.

At this time, the direct current flowing from the reference voltage generating section 5 to Q _33a of the operating high frequency amplifying section is several μm.
It is about A. However, the high frequency amplifier portion 2b in a non-operating state, Q _23b from V _cc during operation, Q _22b, a current which has been flowing through the Q _21B, to several 10μA from several μA to flow from the reference voltage source increases To do.

As a result, a voltage is generated at Q _21b.
Since there is a potential difference between the emitter voltage of _{23a and} the emitter voltage of Q _23b, a fraction of the normal current flows through Q _22b and Q _21b, and the output impedance of the high frequency amplification portion 2b increases.

FIG. 3 shows the output impedance (A1-A1 ') when one high-frequency amplification part is in the operating state, the output impedance (A2-A2') when it is in the non-operating state, and the non-operating state. , the output impedance when applying a same emitter voltage and operating state to the emitter of Q _23b (B1-B1')
Is shown on the Smith diagram.

Here, points A1, A2 and B1 are points at a frequency of 50 MHz, points A1 ', A2' and B1 'are points at a frequency of 5 GHz, and (A2
-A2 ') is the case of the conventional example, and (B1-B1') is the case of the present invention.

As shown in FIG. 3, (A1-A1 ') and (A2-A2)
′) Has almost the same output impedance in the high frequency region, while (A1−A1 ′) and (B1−B1 ′) have higher output impedance in the latter state than in the former state. There is.

FIG. 4 shows the frequency characteristics when the voltage application condition of one high-frequency amplification part is the same as that of FIG. 3, where C1 is the operating state (in the case of a single device), and D1 is the non-operating state of the high-frequency amplification part. When the high frequency amplification part of the state is connected (conventional example), E1
Is the case where the high-frequency amplification part in the operating state is connected to the high-frequency amplification part in the non-operating state (in the case of the present invention).

As shown in FIG. 4, in the case of the present invention, there is almost no effect even if the high frequency amplifying portion in the non-operating state is connected. Next, the operation of FIG. 5 will be described. 2a, 2b, 3a, 3b, and 4 in the figure are the same as the parts having the same reference numerals in FIG.

First, the reference voltage generator 5 generates a predetermined reference voltage using the DC voltage V and applies it to the bi-eye voltage supply portions 3a and 3b via the resistors R _7a and R _7b . The bias voltage supply parts 32a and 32b generate a predetermined bias voltage and supply it to the corresponding high frequency amplification parts 2a and 2b, but as described above, for example, the high frequency amplification part 2b is in a non-operating state.

The two series of high-frequency signals are applied to the high-frequency amplification parts 2a and 2b via the band-pass filters 51a and 51b. The high-frequency signals amplified only by the high-frequency amplification part 2a are mixed via the band-pass filter 54. Send to 53. Mixer
The bias voltage from the mixer bias voltage supply portion 52 is applied to 53, and since the local oscillation signal is also applied via the band pass filter, the high frequency signal is not frequency-converted into an intermediate frequency band signal, which is not shown. It is sent to the latter stage.

That is, according to the first and second aspects of the present invention, the high-frequency switch is not used and the characteristics are not deteriorated.
Since the outputs of the two high-frequency amplification parts can be connected, it is possible to provide a circuit suitable for use as an IC, which can greatly contribute to the reduction of the number of parts and cost.

[0029]

As described in detail above, according to the present invention, there is an effect that the circuit scale can be reduced and a circuit suitable for use in an IC can be provided.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of first and second aspects of the present invention.

FIG. 2 is a configuration diagram of the first and second embodiments of the present invention.

FIG. 3 is an explanatory diagram of output impedance of an amplifier.

FIG. 4 is a gain characteristic diagram of an amplifier.

FIG. 5 is a block diagram of a frequency conversion unit using the second invention.

FIG. 6 is a configuration diagram of a conventional example.

[Explanation of symbols]

2a First high frequency amplification part 2b Second high frequency amplification part 3a First bias voltage supply part 3b Second bias voltage supply part 4 Switching part

Claims (2)

[Claims] 1. An emitter of the first transistor is grounded by a resistor and a collector is grounded by a capacitor, and
The collector of the second transistor is connected to the emitter and the base of the third transistor through a resistor and a capacitor, and the collector of the third transistor is supplied with a DC voltage. The high frequency signal is input to the base of the second transistor and is output from the emitter of the third transistor, and a predetermined high frequency signal is applied by using the first high frequency amplification portion (2a) and the applied reference voltage. And a first bias voltage supply portion (3a) for generating the bias voltage of the first bias voltage supply portion and supplying the bias voltage to the bases of the first to third transistors. Corresponding to the state of the switching signal to be applied, the second high-frequency amplification part (2b) and the second bias voltage supply part (3b) having the same configuration and the same function as the voltage supply part, A switching part (4) for cutting off the supply of one of the DC voltages supplied to the first and second high-frequency amplification parts is provided, and the third part of the first and second high-frequency amplification parts is provided. The emitters of the transistors are directly connected to each other, a high frequency signal is taken out through a DC blocking capacitor, and the reference voltage is applied to both the first and second bias voltage supply portions. High frequency amplifier circuit. 2. The high frequency amplifier circuit according to claim 1, wherein the reference voltage is applied to both of the first and second bias voltage supply parts via first and second resistors.