SU1171973A1 - Tuned amplifier - Google Patents

Abstract

A resonant amplifier containing a first transistor, between the collector of which and the power supply bus includes a load, the first capacitor, one output of which is connected to the collector of the first transistor, the second transistor and the second capacitor, the base of the first transistor being the input of a resonant amplifier, differing from that, in order to ensure linearity and stability of the quality factor when tuning the resonant frequency, two controlled current sources are introduced into it, each of which is connected between the emitter the corresponding transistor and common bus, another output of the first capacitor and the collector of the second transistor are connected to the power supply bus, the collector of the first and the base of the second transistor are combined, and the second capacitor is connected between the I emitters of the transistors, while the load is in the form of connected direct-displaced pn-junctions. from 00

Description

I 1

The invention relates to radio engineering and can be used as a frequency tunable selective device or generator of sinusoidal signals.

The purpose of the invention is to ensure the linearity and stability of the quality factor in the restructuring of the resonant frequency

FIG. 1 is provided, and an electrical principle is applied to the circuit of the proposed resonant amplifier; in fig. 2 - example of use. nor the proposed resonant amplifier as a generator.

The amplifier contains the first and second transistors 1 and 2, the first and second capacitors 3 and 4, the first and second controlled sources 5 and 6 of the current, and the load, executed in the form of a circuit consisting of series-connected direct-displaced pn-junctions, for example diodes 7-9

The amplifier works as follows.

Differential (dynamic) resistances of the emitter pn junction of transistor 1 and pn junction diodes 7-9

g V / i

differential resistance of the emitter pn junction transistor 2

2

where f is the temperature potential,

equal to about 25 mV (at t); i and i, - values of current sources

5 and 6 current.

Let i i i, then r Tj r. Y / i.

 The output signal Ugj is associated with the input signal Ug by the equation

and. . G21 / E ..- 1

2 + T7pCj (Zg + 1 / pc

.. l I ... l I g I

6WX

Where C and C are capacitors 3 and 4, respectively; p is complex variable; the expression in the denominator of the first fraction is the total resistance in the emitter circuit;

719732.

The expression in square brackets is the impedance in the collector circuit of transistor 1.

After the transformation we get 5

UewxC) ZgRSa

Ugjp) 6g2S, + (ZS -fo + 1

Choose C and C so that 10 4C “C, and we denote C C ,, (C + 4C) / 3, then

UffbfxCE) 3.r () 2

6g2S (ZS-le) p2Tg4Sr +

or, taking into account that C, we finally get the transfer function

T, f 9gSr

R (p) - T8g-5T hlp The term r4cp determines the quality factor of the resonant amplifier at the resonance frequency fr

Gain factor equals

Cr 9C / 4C.

Resonant frequency is determined by

by expression

0.0375

P gGTGTGGS gS

taking into account rV / i, we find that the resonant frequency is directly proportional, to the current of controlled current sources f L2: 0.0375, and directly proportional to i.

Temperature stabilization fp

It is not difficult to accomplish by obtaining the same temperature coefficients for i and H (temperature coefficient 1 is about 0, when). Synchronous control of the controlled sources of currents q 2 is easy to implement according to known schemes.

If the capacitance of the capacitor 4 С is chosen somewhat larger than the capacitance C, then the circuit goes into the auto-oscillatory mode at the frequency fp, i.e. becomes a frequency controlled oscillator (Fig. 2).

Instead of Ugj in this case, a constant displacement E, + E is given. The circuit can also be used in other circuits (frequency doubling, phase correction, etc.).

Claims (1)

RESONANT AMPLIFIER, comprising a first transistor, between the collector of which and the power supply bus a load is connected, the first capacitor, one terminal of which is connected to the collector of the first transistor, and the second transistor. a second capacitor, the base of the first transistor being the input of a resonant amplifier, characterized in that, in order to ensure linearity and stability of the quality factor when tuning the resonant frequency, two controlled current sources are introduced into it, each of which is connected between the emitter of the corresponding transistor and the common bus , the other terminal of the first capacitor and the collector of the second transistor are connected to the power supply bus, the collector of the first and the base of the second transistor are combined, and the second capacitor is switched on dy emitters of transistors, wherein the load is configured as a circuit consisting of series-connected forward-biased ρ - η-transitions. The expression in square brackets is the impedance in the collector circuit of the transistor 1. After the transformations we get