JPH05145349A - Power amplifier - Google Patents

Abstract

PURPOSE:To secure the transmission power and to reduce the power consumption without increasing number of components. CONSTITUTION:An amplitude of a signal outputted from a pre-stage circuit is adjusted by a power supply voltage given to the pre-stage circuit and an operating point of a post-stage circuit amplifying and outputting the signal is adjusted by a bias voltage given to a gate of the post stage circuit. When the amplitude of the output of the pre-stage circuit is increased by a power supply voltage given to the pre-stage circuit, the bias given to the gate of the post-stage circuit is controlled to be shallow, on the other hand, when the power voltage given the pre-stage circuit decreases the amplitude of the output of the pre-stage circuit, the bias given to the gate of the post-stage circuit is controlled to de deep.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifier applied to a small radio transmitter / receiver having a shape convenient for carrying, such as a portable telephone.

[0002]

2. Description of the Related Art Recently, for example, portable telephones, which are capable of talking (or transmitting information such as facsimile) from any place whether indoors or outdoors, have become very popular. Since a capacity battery cannot be installed, a circuit configuration that consumes as little battery as possible is required.

Generally, the power consumption of a wireless device is the highest in the power amplification stage. Therefore, when the communication distance (distance from the base station in the case of a mobile phone) is short, the power supply voltage of the power amplification stage is lowered to reduce the transmission power. Is taken, and the operating point of the power amplification stage is always deepened to reduce the idle current (circuit current flowing when transmitting only the carrier).

[0004]

However, if the operating point is always set deeper, it is preferable in terms of power consumption, but on the other hand, there is a drawback that the transmission power is lowered, and the amplification stage must be configured in multiple stages. There have been various problems that the cost increases as the number of points increases, or the yield deteriorates due to the variation in the circuit characteristics due to the increase in the number of parts, and further the circuit scale becomes large and goes against size reduction.

Therefore, an object of the present invention is to secure transmission power and reduce power consumption without increasing the number of parts.

[0006]

In order to achieve the above object, the present invention adjusts the amplitude of a signal output from a pre-stage circuit by a power supply voltage applied to the pre-stage circuit as shown in the principle diagram of FIG. In a power amplifier that adjusts the operating point of the latter-stage circuit that amplifies and outputs the signal by the bias voltage applied to the gate of the latter-stage circuit, the power supply voltage given to the former-stage circuit changes the amplitude of the output of the former-stage circuit. When increasing, the bias applied to the gate of the latter circuit is controlled to be shallow, while when the power supply voltage applied to the former circuit decreases the amplitude of the output of the former circuit, the bias applied to the gate of the latter circuit is deeply controlled. It is characterized by doing.

[0007]

In the present invention, when the power supply voltage applied to the preceding circuit is adjusted and the transmission power changes, the bias voltage of the succeeding circuit (that is, the operating point of the succeeding circuit) is changed according to the change of the transmitting power. .. Therefore, power consumption can be reduced by deepening the operating point during short-distance communication (low power transmission), while sufficient transmission power can be achieved by decreasing the operating point during long-distance communication (high power transmission). Can be secured.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 2 and 3 are diagrams showing a first embodiment of the power amplifier according to the present invention. In FIG. 2, 10 is a front-end circuit, 2
Reference numeral 0 is a post-stage circuit. The pre-stage circuit 10 connects two resistors 11 and 12 in series between the constant voltage Vg ₁₀ and the ground, and combines the voltage appearing across the resistor 12 and the signal input via the coupling capacitor 13. GaAsFE
It is given to the gate electrode of T14 and GaAsFET1
Power supply voltage Vd ₁₀ is applied to the drain electrode of
It is configured by applying a ground potential to the source electrode of the AsFET 14.

The latter circuit 20 has a constant voltage Vg ₂₀ (= Vg ₁₀
2) between the two resistors 21 and 22
Connected in series, the voltage V appearing across the resistor 22
₂₂ (corresponding to the bias voltage described in the gist of the invention) and the pre-stage circuit 10 for inputting through the coupling capacitor 23.
The signal from the above is combined and applied to the gate electrode of the GaAsFET 24, the power supply voltage Vd ₂₀ is applied to the drain electrode of the GaAsFET 24, and the ground potential is applied to the source electrode of the GaAsFET 24.

Here, the coupling capacitor 23, which connects the pre-stage circuit 10 and the post-stage circuit 20 in an alternating current, includes:
A resistor (corresponding to a resistor element described in the gist of the invention) 40 is connected in parallel to form a closed circuit from the power supply voltage Vd ₁₀ of the front stage circuit 10 to the ground through the resistor 40 and the resistor 22 of the rear stage circuit 20. It Current ia flowing in this closed circuit
Direction of the series resistance circuit network (resistor 21,
It is just opposite to the direction of the current ib flowing through the resistor 22).

In such a configuration, the operating point of the GaAsFET 24 of the latter stage circuit 20 is the voltage V across the resistor 22.
Change following ₂₂ . For example, if V ₂₂ is changed in the positive direction, the operating point becomes shallow and a large transmission output is obtained, or if it is changed in the negative direction, the operating point becomes deep and the idle current decreases. The output adjustment of the entire power amplification stage including the pre-stage circuit 10 and the post-stage circuit 20 is performed by adjusting the power supply voltage Vd ₁₀ applied to the pre-stage circuit 10. For example, in the case of long-distance communication, Vd ₁₀ becomes large, and in the case of short-distance communication, Vd ₁₀ becomes small. It should be noted that such power adjustment is generally made automatically based on the received power level.

In this embodiment, the coupling capacitor 2
Since the resistor 40 is connected to 3 in parallel, the bias voltage of the rear circuit 20 can be increased or decreased in response to a change in the power supply voltage Vd ₁₀ of the front circuit 10. This is because the current ia flowing into the resistor 22 of the subsequent circuit 20 changes with the change of Vd ₁₀ , and the voltage V ₂₂ across the resistor ₂₂ (that is, the bias voltage) changes.

Therefore, during long-distance communication, the operating point of the post-stage circuit 20 can be shallowed to obtain a sufficient transmission output, and during short-range communication, the operating point of the post-stage circuit 20 can be deepened. As a result, idle current can be reduced and power consumption can be reduced. FIG. 3 is a graph showing the relationship between transmission power and power consumption. The horizontal axis represents transmission power (Pmax is maximum power, Pmin is minimum power), and the vertical axis is power consumption. Comparing the characteristic line A of the conventional example with the characteristic line B of the present embodiment, P
At max, both power consumptions are about the same, but a large difference occurs as the transmission power becomes smaller. This is because the conventional example has a fixed bias, so that only a single operating point can be set and the operating point cannot be set so deep considering Pmax. On the other hand, in the present embodiment, since the bias changes according to the transmission power, the operating point can be appropriately set appropriately, and the operating point can be deepened and the power consumption can be suppressed as the transmission power decreases. Such power consumption characteristics contribute to the extension of battery life in combination with the usage pattern of the mobile phone. That is, there are not many occasions when the mobile phone is used at the maximum output, and the battery consumption during use of the phone can be suppressed by improving the power consumption in the low / medium output range.

The present invention is limited to the above embodiment.
Of course, various embodiments can be considered.
Is. FIG. 4 shows a second embodiment of the power amplifier according to the present invention.
It is a figure shown, and zener is replaced with resistance 40 of a 1st example.
This is an example of using the diode 50. That is, Kaso
The cathode side is the front stage circuit 10, and the anode side is the rear stage circuit 20.
Connected in parallel to the coupling capacitor 23
Zener diode 50 has Vd_TenAnd V_{twenty two}The potential difference between
If the potential difference is greater than the Zener voltage,
For example, the Zener current ic flows into the resistor 22 of the subsequent circuit 20.
However, if the voltage is less than the Zener voltage, ic is cut off. did
Therefore, Vd_TenIf is large, V depends on ic _{twenty two}Is positive
Direction, and V_TenIc is cut off if is small
V_{twenty two}Is immediately changed to the negative direction.
It Here, V when ic is cut off_{twenty two}Is the size and resistance of ib
It is given by the product of 22.

In addition to the effect of the first embodiment, the present embodiment can make the operating point deep at once when Vd ₁₀ falls below the level determined by the Zener voltage.
For example, it may be suitable for a time division multiplexing portable radio apparatus. In other words, within the time allotted to its own wireless device, the operating point can be adjusted appropriately by flowing the Zener current, and by cutting off the Zener current outside the allotted time, the operating point is deepened to the maximum and consumed. The power can be brought close to zero.

FIG. 5 is a diagram showing a third embodiment of the power amplifier according to the present invention. Two resistors are provided between the power supply voltage Vd ₁₀ of the front stage circuit 10 and the constant bias voltage Vg ₂₀ of the rear stage circuit 20. 60 and 61 are connected in series, the connection point of the resistors 60 and 61 is connected to the base electrode of a bipolar transistor (corresponding to the active element described in the gist of the invention) 62, and Vg ₂₀ is applied to the collector electrode of the transistor 62. The emitter electrode and the gate electrode of the GaAs FET 24 are connected via the resistor 63.

According to this structure, Vd ₁₀ and Vg ₂₀
A voltage corresponding to the potential difference of appears at the connection point of the resistors 60 and 61, and the collector current id of the transistor 62 is controlled by this voltage. Therefore, due to the amplifying action of the transistor 62, it is possible to obtain a change in the operating point larger than the change in Vd ₁₀ , and it is particularly suitable for a wireless device having a large output adjustment range.

[0018]

According to the present invention, since the bias voltage applied to the subsequent circuit is increased or decreased according to the change in the power supply voltage applied to the upstream circuit, the transmission power can be secured without increasing the number of parts. And low power consumption can be achieved.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a configuration diagram of a first embodiment.

FIG. 3 is a graph showing a relationship between transmission power and power consumption according to the first embodiment.

FIG. 4 is a configuration diagram of a second embodiment.

FIG. 5 is a configuration diagram of a third embodiment.

[Explanation of Codes] Vd ₁₀ : Power supply voltage V ₂₂ : Bias voltage 10: Pre-stage circuit 20: Post-stage circuit 40: Resistor (resistive element) 50: Zener diode 62: Bipolar transistor (active element)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Matsumoto 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Masahiro Hirayama, Showa-cho, Nakakoma-gun, Yamanashi 1000-slot, Awahara, Fujitsu Quantum Device Co., Ltd.

Claims (4)

[Claims] 1. An amplitude of a signal output from a front stage circuit is adjusted by a power supply voltage applied to the front stage circuit, and an operating point of a rear stage circuit for amplifying and outputting the signal is applied to a gate of the rear stage circuit. In a power amplifier that is regulated by a bias voltage, when the power supply voltage applied to the preceding circuit increases the amplitude of the output of the preceding circuit, the bias applied to the gate of the following circuit is controlled to be shallow, while the power applied to the preceding circuit is controlled. A power amplifier characterized in that when the voltage reduces the amplitude of the output of the preceding circuit, the bias applied to the gate of the following circuit is deeply controlled. 2. The power amplifier according to claim 1, further comprising a resistance element connected in parallel to a coupling capacitor that connects the output of the front stage circuit and the input of the rear stage circuit. 3. The power amplifier according to claim 1, further comprising a Zener diode connected in parallel to a coupling capacitor that connects the output of the front stage circuit and the input of the rear stage circuit. 4. The power amplifier according to claim 1, further comprising an active element that amplifies a voltage corresponding to a difference voltage between a power supply voltage of the front stage circuit and a predetermined constant voltage to be a bias voltage of the rear stage circuit. .