DE877622C - Circuit arrangement in a television receiver - Google Patents

Description

The invention relates to a circuit arrangement in a television receiver, in which the TV signal that has lost the direct current component in the receiver, with such polarity as Control grid of an amplifier tube is fed that the synchronizing pulses the potential of the Lower the control grid.

If the circuit that contains this amplifier tube forms the last amplifier stage, it must

ίο output signal of this tube, in case it is the anode circuit is removed, fed to the cathode of the cathode ray tube following the tube, since In the anode circuit of the amplifier tube, the synchronizing pulses are positive and the image signals are negative are.

The lost DC component must also be used for proper reproduction of the image be reintroduced, however, proper introduction of the direct current component is only

ao possible if there are disturbances in the input signal, the amplitude of which is that of the synchronization signals exceed, be eliminated.

Such interference limitation could be done at the control grid of the amplifier tube, if this control grid is supplied with such a bias that the vertex of the synchronization signals is just at the cut-off point of the anode current-grid voltage characteristic lie, so that interference signals with a larger amplitude on the amplitude of the synchronizing signals be limited.

A first disadvantage of such a limitation is that the control grid bias of both the image content as well as the signal strength would have to be dependent.

A second disadvantage is that the direct current component has already been reintroduced into this tube so it would be preferable to have the output signal directly from the cathode of the cathode ray tube feed what with regard to the insulation between the cathode and the filament

The high demands placed on the cathode ray tube are usually impossible. One reaches for one non-galvanic coupling, the direct current component must be at the cathode of the cathode ray tube be re-introduced, which is difficult to implement with the aid of the usual diode is because of the unfavorable relationship between the magnitude of the output resistance of the amplifier tube and the small cathode resistance of the electron ίο beam tube.

The circuit according to the invention overcomes these disadvantages and has the feature that the one The signal taken from the output circuit of the amplifier tube in a non-galvanic manner to the cathode of a Electron cathode ray tube supplied and the direct current component in a second output circuit of the amplifier tube is introduced, which is fed to the control grid of the cathode ray tube, and that part of the direct current component that has an effect, which is almost equal to the value of the am Control grid of the amplifier tube occurring AC voltage signals is, in series, with a negative Bias voltage, which almost blocks the amplifier tube in the absence of a signal, the control grid of the Amplifier tube is fed,

- In the circuit according to the invention is so both in the amplifier tube and in the Cathode ray tube introduced the direct current component, which in both cases was almost impossible to achieve Interfering signals is influenced.

The circuit according to the invention is explained in more detail with reference to the drawing.

Fig. Ι shows schematically an embodiment

the circuit according to 'the invention, their mode of operation on the basis of the anode current - control grid voltage - characteristic curve of the shown in FIG Amplifier tube is explained.

In the circuit of FIG. 1, the television signal Vi with the negative polarity of the synchronizing pulses is fed to the control grid of the tube B _{1 via the capacitor C 1} , so that the direct current component is not fed to this control grid. The amplified signal appearing at the anode resistor R _{2 of} the tube B ₁ is fed via the capacitor C _{3 to} the resistor R ₁ inserted in the cathode line of the cathode ray tube B _3.

The amplified signal appearing at resistor R ₂ is also fed to resistor R _{3 via capacitor C 2.}

With the aid of the diode B ₂ and the parallel connection of the capacitor C ₄ and the series-connected resistors R ₄ and R ₅ , the signal appearing at the resistor R ₃ becomes a peak. subject to rectification.

The time constant C ₄ · (A ₄ + R ₅ ) of the parallel connection is preferably about 2 to 10 times. the duration of one line of the television signal.

At the resistors 2? ₄ and R ₅ , the direct current component of the television signal occurs, which after further smoothing with the aid of the resistance-i? ₆ 'urid the capacitor C ₅ ' existing integrating network via the line L to the control grid of the cathode ray tube B _{3 is} fed. - · - - ■ - "

The resistor R ₅ is taken from a voltage that is positive polarity in series with a fixed bias E _{1 of} opposite polarity, which z. B. a battery B _{y is} removed via the resistor R _{1 to} the control grid of the amplifier tube B ₁ .

The fixed, negative bias voltage E ₁ is, as indicated in FIG. 2 on the control grid voltage axis V _g , dimensioned such that the tube B _{1 is} barely conductive in the absence of the input signal F _1.

If an input signal F, - occurs, a voltage will also appear at the resistor R _{5 of} the peak rectifier circuit, as a result of which the control grid voltage of the tube B ₁ becomes less negative.

The resistors R ₃ , i? ₄ and R ₅ are now dimensioned such that, when the input signal Vi has an amplitude E _2, as indicated in Fig. 2, being shown in the rest of the vertices of the synchronizing signal is already at a constant voltage level, and the resistor R ₅ is a DC voltage of the size of E ₂ occurs.

The ratio [R ₄ , -j- ' R ₅ ) IR ₅ must therefore be selected to be almost equal to the voltage gain produced by the amplifier circuit.

As a result, the direct current component is introduced approximately at the control grid of the tube at the time constant C ₄ · (i? ₄ -j- R ₅ ) given above and the vertex of the synchronization signal almost coincides with the blocking point V _{e of} the J _a -F ₅ -Cover characteristic of tube B ₁ .

If interference signals are present, the amplitude of which exceeds that of the synchronization signals these interference signals are then limited to the amplitude of the synchronization signals.

Claims (1)

PATENT CLAIM: Circuit arrangement in a television receiver, in which the television signal in the receiver the DC component has lost, with such polarity the control grid of an amplifier tube is supplied so that the synchronization pulses lower the potential of the control grid, characterized in that the taken from an output circuit of the amplifier tube Signal fed to the cathode of a cathode ray tube in a non-galvanic manner and in a second output circuit of the amplifier tube introduces the direct current component which is fed to the control grid of the cathode ray tube, and that part of the obtained DC component that is almost equal to the value at the control grid of the amplifier tube occurring AC voltage signal is, in series with a negative bias voltage, which is absent of a signal the amplifier tube almost blocks, fed to the control grid of the amplifier tube will. For this 1 sheet of drawing 1 5014 5.53