DE2408991B2 - Oscillator with a transistor in common base - Google Patents

Description

The invention relates to an oscillator with a transistor in common base and positive feedback from a low-resistance tap of an im Collector circuit of the transistor lying on its emitter, in particular on an oscillator for impedance the carrier and / or pilot frequency generation of the carrier frequency technology. ■> ■>

State of the art

Such an oscillator as e.g. B. in FIG. 2 of DD-PS 47 429 is shown and is described in the description, FIG. 1 shows. FIGS. 2a, 2b and 2c ^h ″ show further modifications which can also be attributed to the prior art.

From DE-OS 20 38 435, in particular Fig. Ib with associated text, and from "Funk-Technik", 1972, No. 4, page 132, in particular Fig. 1, oscillators f> 5 are known, although transistors in common base included, but there is no positive feedback from an impedance in the collector circuit of a transistor to its own emitter.

In the oscillator according to DE-OS 20 38 435, F i g. 1 b, the output AC voltage (square wave voltage) of the oscillator, which is taken from the collector circuit of a transistor, rectified and the Base of the same transistor or the base of another transistor supplied. The two transistors form a differential amplifier with collector output circuits and a common emitter resistor.

In the oscillator known from "radio technology", the voltage of a transistor is rectified and fed to the base of the same transistor. This transistor forms with another transistor a differential amplifier with collector output circuits and a common emitter resistor.

task

It is the object of the invention to improve the known oscillator mentioned at the beginning with regard to its amplitude and to improve frequency stability. The oscillator should start to oscillate easily and safely, and the in The distortion products contained in its output signal should be low. Especially in carrier frequency technology becomes not only a high frequency constancy and a high distortion attenuation but also a high one Level constancy z. B. required for the pilot frequency generators.

solution

The object is achieved with the means specified in claim 1.

Further development result from the subclaims.

advantages

The oscillator according to the invention enables very fast adjustment even at very high levels Frequencies. Furthermore, the regulation prevents that when using an oscillating crystal This tension can occur, which can lead to the cracking of the quartz, which is particularly important occurs at high frequencies, i.e. very thin crystals.

advantages

The oscillator according to the invention enables very fast adjustment even at very high levels Frequencies. Furthermore, the regulation prevents that when using an oscillating crystal This tension can occur, which can lead to the cracking of the quartz, which is particularly important occurs at high frequencies, i.e. very thin crystals.

Description of the figures

The invention will now be described in detail using the examples shown in the figures. It shows

Fig. I the known oscillator according to the DD-PS 47,429;

F i g. 2 variants of this oscillator attributable to the prior art;

F i g. 3 shows an example of the oscillator according to the invention with transistors of the same conductivity type;

F i g. 4 shows an example with transistors of different conductivity types;

F i g. 5 shows a variant of the oscillator according to F i r. 3 with

a Spannurigsverdopplerschaltung and a layout for unstabilized supply voltages;

F i g. 6 shows a variant of the oscillator according to FIG. 5 with a transistor as a common emitter resistor;

7 shows the dependency of the oscillator output gnal level from temperature;

8 shows the dependency of the oscillator output signal level from fluctuations in the supply voltage.

Corresponding components have always been used in all figures provided with the same reference numerals.

Fig. 1 now shows the known oscillator from which the invention is based. Trs 1 is a base-connected transistor, the base of which is connected to a bias voltage set via a voltage divider ft 2, ft 3 and the negative voltage via a capacitor C3. Pole (-Uv) of the DC voltage source is connected. In its collector circuit there is a parallel resonance circuit consisting of the coil L. 1 and the capacitor Ci, while the emitter resistor R 1 is arranged in its emitter circuit. The positive feedback path , consisting of the series connection of a quartz crystal Q with an adjustable capacitor C 2, is arranged between a low-resistance tap of the resonant circuit coil L 1 and the emitter of the transistor Trs 1.

The variants of this shown in Fig.2a, 2b and 2c Oscillator will be explained later.

An example of the oscillator according to the invention will now be given with reference to FIGS. 3 explained, where the in τ F i g. 1 is not repeated.

Trs 2 is a collector-operated transistor of the same conductivity type as the transistor Trs X. The emitters of both transistors are connected to one another so that they have the emitter resistor R 1 in common. A decoupling winding is now applied to the coil LX of the parallel resonant circuit, one side of which is at reference potential (ground) and the other end of the winding the output signal A is taken once but also fed to a diode D for half-wave rectification, the rectified voltage being smoothed by means of a charging capacitor C 4 and the base of the transistor Trs 2 is supplied. A resistor R 7 provides the direct current path for the rectifier and base circuit. Similar to a differential amplifier, there is a change in the current distribution between the two transistors ίο Trs X and ^T rs 2 depending on the base voltage of the transistor Trs 2, i.e. depending on the amplitude of the output signal of the oscillator, but this changes as the current increases Trs 2 the output amplitude of the oscillator drops so that it adjusts to a constant value. This value can be z. B. set by changing the base bias of the transistor Trs 1.

FIG. 4 now shows an example of an oscillator according to the invention with two transistors Trs 1 and Trs 2 of different conductivity types. An arrangement according to FIG. 2a was assumed for this configuration. The low-impedance tap of the parallel resonance circuit in the w> collector circuit of the transistor Trs 1 takes place at the connection point of two capacitors CV and Ci " connected in series as a circuit capacitance. This tap is then for the necessary positive feedback via a resistor R 4 e> 5 with the emitter of the Tranr ^; , Stors Trsi . The output signal A is taken from a tap of the parallel circuit coil L 1. The signal present at the collector of the transistor Trs X and thus at the parallel resonance circuit is converted by means of a half-wave rectifier circuit consisting of a diode D, a charging capacitor C4 and a resistor R 7 , rectified, and standing on the charging capacitor CA DC voltage which is proportional to the level of the output signal a, drives the base of transistor Trs 2, in its emitter circuit, an emitter resistor is ft 8 is R 1 is here then once the emitter resistance of the transistor Trs 1 and at the same time the collector resistance of the transistor ors Trs 2. Here, too, the arrangement according to FIG. 3 corresponding control process takes place, the desired output level then in turn being able to be set by changing the base bias voltage of the transistor Trs 1

The oscillator according to the invention according to FIG. 5 corresponds in its basic configuration to that according to FIG. 3, where Trs 1 and Trs 2 are also transistors of the same conductivity type. The peg ?! The control voltage proportional to the output signal A for the base of the transistor Trs 2 is obtained with the help of a known voltage doubler circuit, consisting of diodes D \ and D2, a charging capacitor C 4 and a resistor R 7, which feeds the alternating current signal via a coupling capacitor used for potential separation C5 is fed. This changes the mode of operation of the arrangement compared to that according to FIG. 3 not yet.

From FIG. 3 it can now be seen that, due to the voltage divider R 2, R 3 for the base bias of the transistor Trs 1, the base bias of the transistor Trs 1 and thus the level of the output signal A must also change when the value of the supply voltage Uv changes. So if there is no stabilized supply voltage Uv available, so supply voltage fluctuations must be expected, it is advisable to stabilize the base bias of Trs 1 and thus the level of output signal A by replacing resistor R3 in FIG. 3 with a Zener diode ZX Breakdown voltage is replaced.

6 now shows a further modification of the oscillator circuit according to the invention. This starts from FIG. 2c quartz Q instead of the series circle L. 2, C2 ' in the positive feedback path from FIG. 2b can be seen. Here, too, as in the arrangement according to FIG. 5, the control voltage for the transistor Trs 2 is obtained by doubling the voltage; here, too, the voltage of the base of the transistor Trs 1 is stabilized against fluctuations in the supply voltage Uv by means of a Zener diode ZX. The common emitter resistance of both transistors Trsi and Trs2 now consists of the collector-emitter path of a third transistor Trs 3 and its emitter resistor R 9. This transistor Trs 3 receives its control voltage from the tap of a voltage divider R 3 ', R 3 that is parallel to the Zener diode Z 1 ". the transistor is operated as Konstar'stromquelle to give be Kollekiorstrom then divided depending on the control state of the two transistors TRSi and Trs2. the value of the constant direct current can be effected by changing the voltage divider ratio R 3 ', R 3" or by varying the value of R 9 is set.

Will the base de ?. Transistor Trs3 at point B, / .. B. via a coupling capacitor, not shown, is supplied with an alternating current signal, so the output signal A can be modulated with this as long as the output signal A is formed by the capacitor C4 and the resistor R 7

Zeitkonstantc is so large that this modulating alternating current signal is not also regulated. Such a modulation can also be carried out at the bases of the transistors Trs 1 and Trs2 . This gives the possibility of using the oscillator circuit according to the invention as a self-oscillating mixer stage.

F i g. 7 finally shows the dependence of the level Ui of the output signal A of an oscillator according to the invention on the temperature. When the operating temperature changes from -10 "... +70 ⁰ C, the output voltage changes by less than ± 2% based on an average operating temperature of 30" C. The oscillators of the carrier frequency technology make demands on the level constancy.

F i g. 8 now shows the dependence of the level Uv of the output signal A on fluctuations in the supply voltage Uv, it being assumed that F i ;;. Low dependence within the limits were taken 5 or 6 measures to stabilize the control voltage of the transistor Trs I never ± 20% from the nominal value corresponding to the er'olgendcn with such changes in the Uv Supply voltage changes in the breakdown voltage of the / cnerdiocle Z alone I.

For this purpose 2 sheets of drawings

Claims (6)

Patent claims: 1. Oscillator with a transistor in the base circuit and a positive feedback from a low-resistance tap of an impedance lying in the collector circuit of the transistor on its emitter, in particular oscillator for the carrier and / or Piloifrequen2: - generation of the carrier frequency technology, characterized in that the collector circuit of the The output AC voltage of the oscillator taken from the transistor (Trs 1) is rectified and fed to the base of a further transistor (Trs 2) and that the emitter resistance (R 1) of the first transistor (Trs 1) is at the same time an operating resistance in the output circuit of the second transistor (Trs 2). 2. Oscillator according to claim 1, characterized in that the two transistors (Trs I, Trs 2) have the same conductivity type, that the second transistor (Trs 2) is operated in a collector circuit and that the emitter resistor (R 1) of the first transistor ( Trs 2) is also the emitter resistance of the second transistor (Trs2) (Fig.3, Fig.5). 3. Oscillator according to claim I, characterized in that the two transistors (Trsi, Trs 2) have different Leitfahigkeimyp, since the second transistor (Trs 2) is operated in the emitter circuit and that the emitter resistor (R 1) of the first transistor (Trs i ) also the collector resistance of the second transistor / Trs2) is Jo (Fig. 4). 4. Oscillator according to claim 1, characterized in that the rectification of the output AC voltage by means of a Linwc rectifier (D, C4) takes place (Fig. 3, Fig. 4). J? 5. Oscillator according to claim 1, characterized in that the rectification of the output AC voltage by means of a Spunnungsverdopplerschaliung (D \, D2, C4) takes place (F i g. 5, F i g. 6). 6. Oscillator according to claim 1, characterized in that the common resistor (R 1) consists of the collector-emitter path of a third transistor (Trs 3) operated as a constant current source (FIG. 6). 45