JPH0533060Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention is a power amplifier circuit that can increase stable output compared to conventional circuits and has economic advantages in power circuits of transmitting and receiving devices such as transistors. It is related to.

(Prior Art) FIG. 3 shows an example of a transmission power amplification circuit used in a conventional transceiver, etc., in which three transistors are connected in series. In other words, a signal is input from the input circuit and is amplified by the transistor T _r1 operating in class A, then further amplified by the drive transistor T _r2 operating in class B or C, and the power is increased by the power transistor T _r3 in the final stage. It radiates radio waves from the antenna (ANT). Usually 5
It is configured to obtain an output of ~6W. Note that transistors are generally used to drive the output stage sufficiently.
Both T _r2 and T _r3 are of the same type with Pc (collector loss) of about 10W.

Regarding transceivers and the like, customers want something that can output as high an output as possible because it can be used over a wide range of applications, and those with an output of about 8 to 10 W are preferred. In order to double the output of a conventional device of about 5 to 6 W, 2 to 3 more transistors are required, and the circuit becomes complicated, which naturally increases the cost. It is.
As a solution to this problem, a power amplification circuit has been proposed that uses approximately the same number of components and the same grade of power transistors as the conventional circuit, thereby increasing the output, which is the lifeblood of the transceiver, by nearly twice as much without increasing the cost. has been done. For example, the second
As shown in the figure, the signal is applied from the input circuit to the input amplification stage T _r1 , the drive amplification stage T _r2 , and from the output side of the drive amplification stage to the input circuit of the final output stage, which is the same as in Fig. 3. operate under the conditions. The difference is that, as shown in Figure 2, an output transformer with an intermediate tap is connected between the collectors of the final stage output transistor T _r3 and the drive transistor T _r2 , and a load is connected from the primary or secondary side of the output transformer. By applying positive feedback to the base of T _r2 or the base of the first stage via the impedance Z ₀ , the output is approximately twice that of the amplifier circuit shown in FIG. 3 in total.

The impedance can be a variable impedance so that the impedance value can be adjusted, or it can be a fixed impedance that matches the desired output.

(Problems to be Solved by the Present Invention) The improved high-power circuit of FIG. 2 uses primarily positive feedback means to increase the output. If this circuit is used alone, the operation will tend to become unstable, and if the output is high, there is a high possibility that oscillation will occur. Focusing on this point,
The present invention is an improvement to the more stable power amplification circuit. There are also requests for high output even during transmission.

(Means for solving the problem) In order to eliminate instability such as oscillation that tends to occur when performing the positive feedback, the present invention takes the following technical considerations (1) and (2). . (1) An oscillation suppression and stabilization circuit is provided. This circuit automatically makes the self-bias more negative as the positive feedback voltage increases, allowing the amplification element to operate stably without causing oscillation.

(2) In addition to (1), in order to further improve thermal stability, a generally known bias circuit for temperature compensation is configured and combined to provide comprehensive stability. This is what it aims to do. The present invention improves the commonly used power amplification circuit shown in FIG. 3 as shown in FIG. 2, and also incorporates means for ensuring stability. FIG. 1 shows a simple, high-output, stable power amplifier circuit using the present invention.

(Example) Next, one of the examples using the present invention will be described with reference to FIG. The circuit of this invention is, for example, 1MHz~
It can be used in output circuits such as transceivers that transmit and receive signals in the 300MHz range. Taking the case of sending as an example, specifically,
An input signal of about 150MHz500mV is sent from the input circuit to the next drive transistor via transistor T _r1 .
The output is amplified by T _r2 , and its output is supplied to the final power amplifying element T _r3 via the capacitor C ₇ and the inductance L ₂ , and the output parts of the amplifying elements T _r2 and T _r3 are
An output transformer T ₃ with an intermediate tap is connected, and a resistor R ₆ and a capacitor C ₆ are connected through a variable capacitor Vc that can adjust the amount of positive feedback from the secondary side of the output transformer T _3.
Positive feedback is provided through a CR circuit. The positive feedback variable capacitor Vc and the inductance _L8 are in a state of approximately series resonance, so that a large feedback voltage can be obtained. Further, due to the diode characteristics between the inductance L ₈ , the resistor R ₆ , and the base and emitter of the amplifier T _r2 , the feedback current is rectified by T _r2 and a negative DC voltage is generated in R ₆ . And when the feedback voltage increases, the negative voltage in the R ₆ C ₆ self-bias circuit increases, which lowers the base voltage and increases the amplification element.
It is characterized by being equipped with an oscillation suppression circuit that operates to maintain T _r2 stably. Therefore, the feedback adjustment is made more stable. Next, although it is generally used, in the case of Fig. 1, a bias circuit D ₁ and C ₀ consisting of three amplifying elements and a diode D ₁ is provided and combined as a temperature compensation stabilizing circuit. The feature of the present invention is that the positive feedback power amplification circuit is made ultra-stable. As mentioned above, the transistors T _r2 and T _r3 are power type transistors of the same grade and are operated in class B or C, and the transistor T _r1 is normally operated in class A.

Further, although FIG. 1 shows an example in which a transistor is used in the circuit according to the present invention, it goes without saying that the present invention can be applied to all available amplifier active elements such as vacuum tubes in addition to transistors.

(Effects of the invention) As described above, in this invention, a high frequency power amplification circuit consisting of about three transistors such as a transceiver is connected in series and an output transformer with an intermediate tap is provided on the output side of the latter two stages. The performance of the amplifier circuit is that it can operate in class B to class C, provide positive feedback to the input from the output transformer's secondary side, and adjust the amount of feedback to obtain an output of about 8 to 10 W. In order to achieve even more stable operation, an oscillation suppression circuit and a temperature compensation bias circuit are also installed, making it possible to not only stably obtain a high output of 8 to 10W as a 3-stage power amplification circuit, but also It is possible to practically obtain a low-cost high-frequency power circuit without increasing the number of parts, and the effects of the present invention can be said to be extremely significant industrially.

[Brief explanation of the drawing]

Fig. 1 shows an example of the power amplification circuit according to the present invention, and Fig. 2 shows an improvement on the conventional power amplification circuit Fig. 3;
This invention is based on the present invention, which is a further improvement to the power amplification circuit shown in the figure. T _r1 ... Transistor, T _r2 , T _r3 ... Power transistor, Z ₀ ... Variable impedance, Vc...
…Variable capacitance, T ₁ … Output transformer, T ₂ , T ₃ …
Push-pull type output transformer, C ₁ , C ₃ , C ₇ ...
DC blocking capacity, L ₁ , L ₂ , L ₃ , L ₄ , L ₅ , L ₆ , L ₇ ,
L ₈ ...Inductance, R ₀ , R ₁ , R ₂ , R ₃ , R ₄ ,
R ₅ , R ₆ ... Resistance, C ₀ , C ₂ , C ₄ , C 5 , _{C 6 ...} Capacitance, ANT ... Antenna, ... Input circuit, D ₁ ... Diode, R ₆ , C ₆ Parallel circuit...Oscillation suppression self-bias circuit, C ₀ , D ₁ parallel circuit...
Bias circuit for temperature compensation.

Claims (1)

[Scope of utility model registration request] Amplifying active elements such as transistors (hereinafter referred to as elements) are used to configure at least a three-stage amplifier circuit, and the final output element of the output stage and the element in the previous stage are both equivalent elements, and The elements are connected to drive the final stage output element, the final stage output element and the previous stage element are both biased to class B or class C, and the output parts of these two elements are connected to an output transformer to further output 1st and 2nd order of transformer
Positive feedback is applied from the next side to the input side of the previous stage element or the input side of the previous stage, and the voltage applied to the self-bias circuit changes depending on the magnitude of the positive feedback voltage, thereby stabilizing the bias voltage on the input side. 1. A power amplifying circuit comprising an oscillation suppressing circuit having a self-bias circuit including a feedback resistor R and a capacitor C connected in parallel with the feedback resistor R, which stably operates an amplifying element.