JPH06152263A - Amplifier - Google Patents

Abstract

PURPOSE:To improve the frequency characteristic in a high band with a simple constitution by providing voltage and current feedback means between the first stage and the last stage of an amplifying circuit. CONSTITUTION:The base earth circuit of a transistor TR Q2 is cascaded to the emitter earth circuit of a TR Q1 in the first stage of the amplifying circuit and the low impedance of the base circuit of the TR Q2 is taken as the load of the TR Q1 to improve the high-band frequency characteristic. Further, the emitter earth circuit of the TR Q3 is cascaded, and a voltage series feedback resistance R1 is connected between the collector of the TR Q3 and the emitter of the TR Q1, and a current parallel feedback resistance R3 is connected between the emitter of the TR Q3 and the base of the TR Q1, thus constituting a composite multi-feedback circuit. Thus, the frequency characteristic in the high band is improved with the simple circuit constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifier, and more particularly to a high frequency wide band transistor amplifier circuit.

[0002]

2. Description of the Related Art In a conventional bipolar transistor amplifier, particularly a high-frequency multi-feedback broadband amplifier, a first-stage grounded-emitter circuit and a final-stage grounded-emitter circuit are connected in cascade, and an emitter and a final-stage emitter-grounded circuit are connected. There is a circuit in which a voltage series feedback resistor is connected between the collector of the stage grounded-emitter circuit and a current parallel feedback resistor is connected between the base of the first stage grounded-emitter circuit and the emitter of the final stage grounded-emitter circuit. It was In this transistor amplifier, the impedance matching of the input / output portion is performed, and it is intended to have a gain-frequency characteristic in a wide band.

[0003]

In the above-described conventional transistor amplifier, since the first-stage and the last-stage grounded emitter circuits are connected in cascade, the input impedance of the last-stage emitter grounded circuit is equal to that of the first-stage emitter grounded circuit. Since it is a load and its value is high and the first stage is a grounded-emitter circuit, the collector-base capacitance Ccs serves as a feedback capacitance from the collector to the emitter to produce the Miller effect, and the frequency characteristic in the high range. There was a problem that it deteriorated.

The object of the present invention is to solve the above problems.
It is an object of the present invention to provide an amplifier having improved frequency characteristics in a high frequency band with a simple structure.

[0005]

The amplifier of the present invention has a first grounded-emitter circuit, a grounded-base circuit cascade-connected to the first grounded-emitter circuit, and a cascade connection to the grounded-base circuit. A second grounded-emitter circuit and means for feeding back voltage and current from the second grounded-emitter circuit to the first grounded-emitter are provided.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a main part of an amplifier according to a first embodiment of the present invention. FIG. 1 shows an embodiment in which only NPN type bipolar transistors are used as transistors. The bias circuit is omitted.

The transistor amplifier of this embodiment is connected in cascade with a transistor Q1, a current series feedback resistor composed of an emitter resistor R2 having one end connected to the emitter of the transistor Q1 and the other end grounded. A feedback resistor R connected between the collector, which is the output electrode of the grounded base circuit of the transistor Q2, and the output electrode of the grounded emitter circuit of the transistor Q3, which is cascade-connected to the base ground circuit, and the emitter of the transistor Q1.
A voltage series feedback resistor composed of 1 and a current parallel feedback resistor composed of a resistor R3 connected between the emitter of the final-stage grounded-emitter circuit and the base as an input electrode of the first-stage grounded-emitter circuit. I have it.

Further, a resistor R4 is connected between the emitter of the transistor Q3 and the ground to connect the transistors Q1 and Q1.
Resistors R5 and R6 are connected between the collector of No. 3 and the power supply VCC terminal, respectively.

Next, the operation of this embodiment will be described.
By connecting the grounded base circuit of the transistor Q2 in cascade to the grounded emitter circuit of the transistor Q1, the high-frequency characteristic is significantly improved as compared with the case of the grounded emitter circuit of the transistor Q1 alone. The reason is that the grounded base circuit of the transistor Q2 has a low input impedance and acts as a load for the grounded emitter circuit of the transistor Q1.
The grounded-emitter circuit formed by the transistor Q1 and the grounded-base circuit formed by the transistor Q2 connected in cascade are connected as a single circuit, and the grounded-emitter circuit formed by the transistor Q3 is connected in cascade. By connecting the series feedback resistor R1 and connecting the current parallel feedback resistor R3 between the emitter of the transistor Q3 and the base of the transistor Q1, a composite multi-feedback circuit configuration is obtained, and the frequency characteristics in the high frequency range are improved. We are making improvements.

FIG. 2 is a circuit diagram showing an amplifier according to the second embodiment of the present invention. In FIG. 2, the amplifier of the second embodiment is a circuit in which peaking capacitors C1 and C2 are connected in parallel with the resistors R2 and R4 of the circuit of FIG.

In FIG. 2, in order to further improve the frequency characteristic in the high frequency range, the emitter resistances R2 and R4 of the transistor Q1 and the transistor Q3 are compared with the circuit of FIG.
In this example, the emitter peaking capacitors C1 and C2 are connected in parallel.

FIG. 3 shows the circuit of the second embodiment of FIG.
It is a circuit diagram which shows the 3rd Example comprised with the P-type transistor. In FIG. 3, the operation of this embodiment is similar to that of FIG. By removing the capacitors C1 and C2 of FIG.
This circuit is the same as that of the circuit of PNP transistor.

Although FIGS. 1 and 2 show the NPN type transistor, a PNP type transistor can also be used.
A field effect transistor may be used instead of the bipolar transistor. In this case, the collector, emitter, and base of the transistor are replaced with the drain, source, and gate of the field effect transistor, respectively, and the other circuit parts are the same as those in FIGS. 1 and 2.

As described above, according to the present invention, for example, the collector (drain) of the first-stage emitter (source) ground circuit and the base (gate) of the last-stage emitter (source) ground circuit are connected in cascade. Insert a base (gate) ground circuit between them, and a collector (drain) and a first stage emitter (source) of the final stage emitter (source) ground circuit
An amplifier in which a voltage series feedback resistor is connected between the ground circuit emitter (source) and a current parallel feedback resistor is connected between the first stage base (gate) and the final stage emitter (source), In order to improve the high frequency characteristic of the conventional multi-feedback amplifier, it can be manufactured at a low cost with a simple structure.

[0015]

As described above, according to the present invention,
By providing the voltage / current feedback means and the like, it is possible to obtain an effect that the high frequency characteristic can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an amplifier according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention.

[Explanation of symbols]

 Q1, Q2, Q3 transistors C1, C2 capacitors R1, R2, R3, R4, R5, R6 resistors

Claims (2)

[Claims] 1. A first grounded-emitter circuit, a base-grounded circuit cascade-connected to the first grounded-emitter circuit, a second grounded-emitter circuit cascade-connected to the base-grounded circuit, and the second Means for feeding back voltage and current from the grounded-emitter circuit to the first grounded emitter. 2. The amplifier according to claim 1, wherein the first and second grounded-emitter circuits each include a peaking capacitor.