DE1104571B - HF input stage with two triode systems - Google Patents

Description

GERMAN

The invention relates to an RF input stage with two triode systems for radio and television receivers, whose first triode is connected in a grid-base circuit to the receiving antenna and its anode can be capacitively switched to the grid of the second triode and with one connected to this grid Resonant circuit is provided with adjustable capacitance and a self-induction to which the antenna is used Reception of amplitude-modulated broadcasts can be switched with separation from the first triode.

The invention provides an improvement of such circuits in that the self-induction a Has adjustable tap for the cathode negative feedback lying at a fixed potential and between the anode of the first and the cathode of the second triode is connected while they are via the center tap is turned on in the DC power supply circuit of the first triode.

This circuit is characterized by the fact that it has an auto-neutrodyne effect over a large bandwidth owns, whereby it allows different bandwidths by adjusting the tap on the tuning coil to receive. Furthermore, by using only one tube, the Negative coupling connections and thus an essential higher gain achieved.

According to a further feature of the invention it is provided that the self-induction such The sense of the winding is that the resonance circuit in the event of changes in the cathode potential is caused by the one acting on the grid Control voltage presses this grid corresponding anti-phase voltage, which is a magnetic Counteraction with a broadening of the passage width and a static counteraction of the resonance circuit capacitance to suppress wild vibrations caused by the grid-anode capacitance.

A cathode current coupling with a tapped input circuit has become known, in which the between Grid and cathode switched negative feedback tuning coil with a grounded tap is provided. A capacitor is connected in parallel to this tuning coil. Meanwhile, with this circuit a neutralization capacitor is provided so that this circuit can be reduced by the use of a Capacitor for the neutralization occurring disadvantages such. B. Reduction in performance, limitation the bandwidth, etc. This circuit has attempted to create a low-noise RF stage to create with a single triode system. A suggestion for solving the reasons for the invention task to create a circuit for radio and television reception that makes it possible to with a large bandwidth with high and constant performance and a single setting for all HF input stage with two triode systems

Applicant: Sautier & Jaeger, Geneva (Switzerland)

Representative: Dipl.-Ing. R. Müller-Börner, patent attorney, Berlin-Dahlem, Podbielskiallee 68

Claimed priority: Switzerland of January 26, 1954

Bandwidths to neutralize the harmful capacitance between grid and anode, the autoneutrodyne effect Using the negative feedback circuit is not an obvious choice.

In the drawing, the invention is illustrated using an exemplary embodiment. It shows Fig. 1 is a diagram of a high frequency stage and

FIG. 2 shows a theoretical diagram for explaining part of the circuit according to FIG. 1.

The receiver intended for recording the very different frequency ranges contains ■ - in the high frequency - controllable and divided capacitor groups, ie capacitors CV _t with a small maximum capacity for television ultra-short waves and for broadcasts with frequency modulation and capacitors CV ₁ - larger maximum capacity.

The high-frequency stage shown in Fig. 1 shows a directional antenna B ₁ which is connected to the cathode resistor rc of a first triode with a grounded grid ^ ₁ . This first triode with grid g _t and a second triode with cathode C ₂ and anode p _z are combined to form a tube E. The winding of the induction coil se of the tuning circuit has a tap 77 which is adjustable and connected to ground via a capacitor cm. The anode p _{x of} the first triode is connected to the grid ^ _{2 of} the second triode via the capacitor ei. The tap 77 for the cathode negative feedback is based on the principle of magnetic and static negative feedback, which is explained using the theoretical scheme in FIG.

It is assumed that the tap 77 is grounded and is thus at zero potential. If that

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Grid g. ₂ becomes positive, the cathode c ₉ becomes positive to ground. This positive potential is transferred to the end A of the induction coil se. However, due to the winding direction of the coil, this is a negative voltage (-), which is impressed on the grid g _o via the other end / i "of the coil. This voltage is therefore in Antiphase to the received voltage: There is a magnetic negative coupling through the coils, which causes the transmitted tape to sag.

On the other hand, as in all triode stages, the internal harmful capacitance Cgp between grid and anode feeds back to the grid an increased energy in phase with the control voltage Vg. The triode thus runs the risk of oscillating if the capacitance CV does not correspond to the grid g. ₂ would impose a negative voltage opposite to the amplified energy originating from Cpg. An autoneutrodyne effect and a static negative feedback are thus brought about.

The self-inductive and capacitive effects explained above tend to remain constant over a large frequency range due to the reverse phase shifts achieved by se and cv.

The neutrodyne effect extends over a wide range. The bandwidth to be received is determined by adjusting the tap 77 on the tuning coil se . As this tap approaches the TLndeA , the selectivity increases and the risk of entrainment increases. Conversely, when the tap 77 approaches the point H , the bandwidth becomes wider depending on the increase in the negative feedback.

Triode connected in a grid-base circuit to the receiving antenna and whose anode can be capacitively switched to the grid of the second triode, and with a resonant circuit connected to this grid with adjustable capacitance and a self-induction, to which the antenna for receiving amplitude-modulated transmissions is separated from the first triode is switchable. characterized in that the self-induction (se) has an adjustable tap (77) at a fixed potential for the cathode negative feedback and is connected between the anode (P ₁ ) of the first and the cathode (c ₂ ) of the second triode, while it is connected via the Center tap (77) is switched on in the DC power supply circuit of the first triode.

2. RF input stage according to claim 1, characterized in that the self-induction (se) has such a winding sense that the resonance circuit (se, cv) at cathode potential changes by the control voltage acting on the grid pushes this grid corresponding antiphase voltages, which a magnetic counteraction with a broadening of the passage width and a static counteraction of the resonance circuit capacitance to suppress wild oscillations caused by the grid-anode capacitance.

Claims (1)

Patent claims: 1. HF input stage with two triode systems for radio and television receivers, the first of which 35 Publications considered:
German Patent No. 740120;
French Patent No. 863,263;
U.S. Patent No. 2,295,383;
Philips Technical Review, September 1949,
Volume 3, p. 92; Radiotechnik, 1951, No. 11, pp. 474 to 476;
Telefunken tube, 1953, issue 30, pp. 52 to 54. 1 sheet of drawings © 109 540/306 4.