JPS5894210A - Internal matching type high-frequency transistor - Google Patents

Abstract

PURPOSE:To amplify only a desired frequency band for an internal matching type high-frequency transistor consisting of a transistor and the 1st and 2nd matching circuits, by connecting an HPF between an input terminal and the 1st matching circuit. CONSTITUTION:An internal matching high-frequency transistor is provided with a transistor TR1, the 1st matching circuit 10 connected between an input terminal 2 and the base of the TR1, and the 2nd matching circuit 11 connected between an output terminal 6 and the collector of the TR1. Then an HPF15 consisting of coils 12 and 13 and a capacitor 14 is connected between the terminal 2 and the circuit 10. In such constitution, if the frequency component less than a desired frequency is contained in the input signal which is fed to the terminal 2, this component is greatly attenuated by the HPF15. This component improves the spurious characteristics of an amplifier. Then unstable working can be eliminated by using such internal matching type high-frequency transistor to form an amplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stable internally matched high frequency transistor.

Usually, a matching circuit for an internally matched high-frequency transistor has a configuration of a hybrid integrated circuit or a monolithic integrated circuit, and the circuit shown in FIG. 1 is generally not used. That is, FIG. 1 is a circuit diagram showing a conventional internally matched high frequency transistor.

In the same figure, (11 is a transistor, (2) is an input terminal, (3) is a first capacitor connected between this input terminal (2) and the ground, (41ti is the transistor (1)
) a second capacitor connected between the base of
(5) represents the input terminal (2) and the transistor (1);
The first coil connected between the base and the output terminal (6) is +71Fi.

A third capacitor (8) is connected between the collector of the transistor (1) and the ground, (8) is a fourth capacitor connected between the output terminal (6) and the ground, and (9) is the transistor (1). This is a second coil connected between the collector of and the output terminal (61).

Note that a first matching circuit in the form of a low-pass filter (hereinafter referred to as LPF) is constructed of the first capacitor (3), the second capacitor (4), and the first coil (5), and constitutes an LPF type second matching circuit including the third capacitor (7), the fourth capacitor (8), and the second coil (9).

Next, in the internal matching type high frequency transistor having the above configuration, the LPF type first matching circuit (1o) is connected to the transistor (
The input impedance of 1) and the output impedance of the signal source or previous stage connected to the input terminal (2) are matched in a desired frequency band. Further, the LPF type second matching circuit 0υ matches the output impedance of the transistor (1) and the input impedance of the load or subsequent stage in a desired frequency band.

However, conventional internally matched high-frequency transistors not only have a large gain in a target frequency band, but also have a considerably large gain in a lower frequency band. This is because the gain of the transistor itself increases significantly as the frequency decreases, so even if the first Mk combining circuit On and the second matching circuit 0υ become mismatched outside the desired frequency band, a considerable gain is generated as a whole. It is from. Therefore, when an amplifier is constructed using such internally matched high-frequency transistors, not only is the operation likely to become unstable, but also the signal source and output of the previous stage may contain frequency components below the desired frequency. This has the disadvantage that this signal is amplified and deteriorates the spurious characteristics of the entire amplifier.

Therefore, an object of the present invention is to provide an internally matched high frequency transistor that can amplify only a desired frequency band.

In order to achieve such an object, the present invention connects a high-pass filter between the input terminal and the first matching circuit. FIG. 1 is a circuit diagram showing an embodiment of an internally matched high-frequency transistor according to the invention. In the same figure, Ql [
The third coil 01 is connected between one end of the coil (5) and the ground, the fourth coil is connected between the input terminal (2) and the ground, Q41Fi, Jl is the third coil connected between one end of the coil f51 and the input terminal (2). ) is the fifth capacitor connected between the

Nao, α9 is the third coil α2. It is composed of the fourth coil (13 O and the fifth condenser A41), and the input terminal (2
) and the first matching circuit 00) is a high-pass filter (hereinafter referred to as HPF).

Next, in the internally matched high-frequency transistor with the above configuration, even if the input signal input to the input terminal (2) contains a frequency component below the target frequency, the soft component Fi
HPFQ5) Attenuates significantly more than K.

Therefore, the spurious characteristics of the amplifier are improved.

Therefore, by constructing an amplifier using this internally shaped high-frequency transistor, instability in operation can be eliminated.

In addition, in the above embodiment, Hpp(t5 is replaced by the third coil (J
Although the configuration is shown in which the fourth coil Q3 and the fifth capacitor θ4 are used, the present invention is not limited to this, and it goes without saying that various configurations may be used.

As described above in detail, according to the internally matched high-frequency transistor according to the present invention, the gain can be significantly reduced in the frequency band below the target frequency band. Therefore, when an amplifier is constructed using this internally matched high-frequency transistor, the operation can be stabilized, and the spurious characteristics of the amplifier can be improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional internally matched high frequency transistor, and FIG. 2 is a circuit diagram showing an embodiment of the internally matched high frequency transistor according to the present invention. (11... fist transistor, (2)... fist input terminal, (3)... first capacitor, (41... second
Capacitor, (51... 1st coil, (61-...
・Output terminal, (7)...Third capacitor, (8)・
...Fourth capacitor, (9)...Second coil, (
1 fall...first matching circuit, Qll...second matching circuit, Q? J・e・3rd coil, 03)-・fist 4th coil, 141・・5th capacitor, 09 fist...
High pass filter. Note that the same reference numerals indicate the same or equivalent parts. Agent Shin Kuzuno - (1 other person)

Claims (1)

[Claims] a transistor, a first matching circuit of the low-pass filter type connected between the input terminal and the base of the transistor, and a second matching circuit of the low-pass filter type connected between the output terminal and the collector of the transistor. 1. An internally matched high-frequency transistor comprising a circuit, characterized in that a high-pass filter is connected between the input terminal and the first matching circuit.