JPS61134107A - Amplifier - Google Patents

Abstract

PURPOSE:To obtain a high frequency, high band amplifier free from decrease of gain in low band by connecting a series circuit of a loop feedback resistance and a capacitor between the collector of a base grounding circuit and the base of an emitter grounding circuit and making the product of the value of capacity of the capacitor and working frequency width less than a specified value. CONSTITUTION:The collector terminal 22 of a base grounding Tr20 and the base terminal 11 of an emitter grounding Tr10 are connected in series by a loop feedback resistance 40 and a capacitor 50 for low band gain control. In this case, the capacity value of the capacitor 50 is so determined that inverse number of product of working frequency width of an amplifier and value of capacity of the capacitor 50 has a value greater than 20. By selecting above- mentioned value properly within a forementioned range, the quantity in low band can be adjusted. Accordingly, increase of loss in low band due to reduction of number of winding of a load transformer 60 for widening band of the amplifier can be compensated by adjusting the value of capacity of the capacitor 50.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an amplifier, and particularly to a high frequency broadband amplifier.

[Conventional technology]

Conventionally, in amplifiers, especially high-frequency loop feedback wideband amplifiers, a first stage common emitter circuit and a final stage common base circuit are connected in cascade, and the collector of the common base circuit and the base of the common emitter circuit are connected in cascade. A series circuit with a loop feedback resistor and a capacitor is connected to the transformer, which has an inductance of gold as a load.

[Problems that the invention attempts to solve]

In the conventional amplifier described above, the reciprocal of the product of the capacitance value of the capacitor connected in series with the loop feedback resistor and the operating frequency width of the amplifier is set small. Therefore, in order to extend the frequency band of an amplifier, if you reduce the number of turns of the transformer connected as a load to widen the band, the characteristics of the transformer will deviate from the ideal transformer characteristics in the low frequency band of the amplifier. This has the disadvantage that the loss in the amplifier increases, and therefore the low-frequency gain of the amplifier decreases.

An object of the present invention is to obtain a high frequency/high band amplifier in which the gain does not decrease in the low range.

[Means for solving problems]

That is, the amplifier of the present invention is a circuit in which a common emitter circuit and a common base circuit are connected in cascade, and in an amplifier having an inductance component as a load, a loop is provided between the collector of the grounded pace circuit and the base of the common emitter circuit. A series circuit of a feedback resistor and a capacitor is connected, and the reciprocal of the product of the capacitance value of the capacitor and the frequency width used has a value of 20 or more.

〔Example〕

A detailed explanation will be given below using all the drawings.

FIG. 1 is an equivalent circuit diagram of a water amplifier according to an embodiment of the present invention. A feedback resistor 30 is connected in series to the emitter terminal portion 13 of the first transistor 10 whose emitter is grounded, and is grounded to the ground portion 70 .

'*7'C1 7th' transistor collector terminal part 12
, the emitter of the second transistor 20, and the terminal portion 23 are connected in cascade. The transistor 20 of WX2 is a common base type fJ, and the base terminal part 21 is the ground part 70.
and has a transformer 60 as a load. Further, the collector terminal portion 22 of the second transistor 20 and the base terminal portion 11 of the first transistor 100 are connected to a loop feedback resistor 40 and a capacitor 50 for low-frequency gain control.
They are connected in series.

The capacitance value of the capacitor 50 is determined so that the reciprocal of the product of the frequency range used by the amplifier and the capacitance value of the capacitor 50 is 20 or more, and in order to improve the gain flattening characteristics of the amplifier, It is set so as to obtain the gain value of , and becomes the friend value. That is, by adjusting the capacitance value t of the capacitor 50, the amount of feedback of the amplifier, especially in the low frequency range, can be adjusted.
For example, if the capacitance value is increased, the feedback amount will increase, and if the capacitance value is decreased, the feedback amount will be decreased. Specifically, 50
0MHz? In an amplifier that has a bandwidth of 1F and uses a toroidal core with μ=300 and a wire T-3 winding transformer with a wire diameter of 0.16φ, the capacitance value of the low-frequency gain control capacitor 50 is 1QPF~ It becomes 20PF.

〔Effect of the invention〕

As explained above, in the present invention, the reciprocal of the product of the capacitance 11 ft-1 of the low-frequency gain control capacitor 50 and the operating frequency width is appropriately selected in the range of 20 or more, and the low-frequency feedback of the amplifier Therefore, in order to make the amplifier wider, the loss in the low range increases due to the reduction in the number of turns of the transformer 60, There are effects that can be compensated for.

[Brief explanation of the drawing]

FIG. 1 is an equivalent circuit showing one embodiment of the present invention. 10...First transistor, 11...
・Pace terminal part of the first transistor, 12...
・Collector terminal part of the first transistor, 13...
・Emitter terminal part of the first transistor, 20...
... second transistor, 21 .... second transistor's pace terminal section, 22 ..... second transistor's collector "flS", 23 ..... second transistor The emitter terminal part of the transistor, 30...
Emitter resistance, 40...Loop feedback resistance, 50...
...Low frequency gain control capacitor, 60.
...Transformer, 70...Grounding section.

Claims (1)

[Claims] In an amplifier which is a circuit in which a common emitter circuit and a common base circuit are connected in cascade and has an inductance component as a load, a loop feedback resistor and a capacitor are connected between the output terminal of the common base circuit and the input terminal of the common emitter circuit. 1. An amplifier connected to a series circuit, wherein the reciprocal of the product of the capacitance value of the capacitor and the operating frequency width has a value of 20 or more.