JPH03270307A - Transistor amplifier - Google Patents

Abstract

PURPOSE:To realize the transistor(TR) amplifier capable of dividing frequency band into two for amplification with use of one amplifier by grounding the emitter of the TR, providing a resonance circuit element between its collector and base and between its emitter and ground, and differentiating the resonance frequency of the resonance circuit elements. CONSTITUTION:A series resonance circuit element comprising an inductor L1 and a capacitor C1 is connected in parallel with a voltage feedback resistor R1, between the emitter and the ground of a TR Q1. Moreover, a series resonance circuit element comprising an inductor L2 and a capacitor C2 is connected in parallel with a voltage feedback resistor R2 between the collector and the base. In such a case, the resonance frequency of the resonance circuit elements in this circuit constitution is made different from each other to divide the utility band of the TR amplifier into two. Thus, one transistor amplifier whose gain and frequency characteristic is divided into two is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to transistor amplifiers, particularly band-splitting high frequency transistor amplifiers.

[Prior Art] Conventionally, two types of circuits have been used as transistor high frequency amplifiers: one that maximizes the gain at a single frequency, and one that has broadband frequency characteristics due to resistive feedback.

[Problem to be Solved by the Invention 1] When amplifying two frequency bands, two amplifiers are connected in series in a single-frequency type. Furthermore, in the broadband type, a bandpass filter or notch filter is inserted before or after one amplifier. This has the drawback of making the circuit complex and expensive.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a transistor amplifier with a novel configuration that can divide and amplify two frequency bands with one amplifier.

[Means to solve problems]

The amplifier of the present invention has a transistor whose emitter is grounded, a voltage feedback resistor with a parallel resonant circuit element connected in series between its collector and base, and a voltage feedback resistor with a series resonant circuit element connected in parallel between its emitter and ground. A feedback resistor is provided to vary the resonant frequencies of the resonant circuit elements.

[For production]

If there is no resonant circuit element with only a voltage feedback resistor and a current feedback resistor, the transistor amplifier has flat characteristics with constant gain. However, when a resonant circuit element is provided, the resistance value of the current feedback resistor becomes effectively low and the resistance value of the voltage feedback resistor effectively becomes high in the vicinity of each resonant frequency. This makes it possible to obtain resonant gain characteristics in the vicinity of each resonant frequency. Therefore, one amplifier can handle the two divided frequency bands.

[Examples] Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of the first embodiment. As shown in the figure, in this embodiment, a series resonant circuit element consisting of an inductance LIS and a capacitor C1 is connected in parallel with an electromagnetic feedback resistor R1 between the emitter of a transistor Q and ground. In addition, there is an inductance L2 between the collector and the base.
A parallel resonant circuit element consisting of a capacitor C2 and a capacitor C2 is connected in series to a voltage feedback resistor R2. By making the resonant frequencies of the resonant circuit elements different in the above circuit configuration, the gain band of the transistor amplifier can be changed to 2 as shown by the solid line in Figure 2.
It can be divided into two parts.

As shown in Figure 2, if there is no return path, that is, R2
When = ■, R, = O, the gain/frequency characteristics are A.
become that way. On the other hand, when there is no resonant circuit element, the feedback amplification characteristic with only the current feedback resistor R and the voltage feedback resistor R becomes a flat characteristic as shown in B. Currently, VHF band [30MHz~30OMHzl] and UHF band (470MHz
MH2 to 900MHz), the resonant frequency of the series resonant circuit element consisting of inductance Ll + capacitor C1 is approximately 165 MHz, and the resonant frequency of the parallel resonant circuit element consisting of inductance La and capacitor C2 is approximately 685 MHz. . Therefore VH
In the F band, current feedback decreases.

As shown by C1, the gain increases around the resonant frequency (approximately 165 MHz). On the other hand, in the UHF band, the voltage feedback decreases and the resonant frequency (approximately 685 MHz) increases as shown by C2.
Gain increases around . In this way, C in Fig. 2,
As shown in C, separated frequency gain characteristics are obtained. Note that in FIG. 1, the bias circuit is omitted and not shown.

Next, a second embodiment will be described with reference to FIG.

The difference from the first embodiment is that the current feedback path including the resistor R3 is provided with emitter peaking by the capacitor C3, and the voltage feedback path including the resistor R2 is provided with an inductance L3.
The problem is that the picking is a mistake. This allows the band of gain and frequency characteristics on the high frequency side to be extended.

[Effects of the Invention] As explained above, in the emitter-grounded transistor amplifier according to the present invention, the current feedback path between the emitter and the ground and the voltage feedback path between the collector and the base each have resonant frequency characteristics using resonant circuit elements. As a result, it is configured to have gain/frequency characteristics that divide the frequency band into two. As a result, it is a single transistor amplifier, and there is no need to use a bandpass filter or notch filter for frequency band division as in conventional examples, resulting in the simplest circuit configuration and the advantage of being able to be manufactured at low cost. There is.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention, FIG. 2 is a gain/frequency characteristic diagram, and FIG. 3 is a circuit diagram of another embodiment. Ql--Transistor, C3-C3...Capacitor, L1-L3...Inductance, R1-Current feedback resistance, R2...Voltage feedback resistance.

Claims (1)

[Claims] A transistor whose emitter is grounded, a voltage feedback resistor with a parallel resonant circuit element connected in series between its collector and base, and a current feedback resistor with a series resonant circuit element connected in parallel between its emitter and ground, A transistor amplifier characterized in that the resonant frequencies of resonant circuit elements are made different.