DE1015947B - Amplifier tubes with high electronic input resistance - Google Patents

Description

In electron tubes that are intensity-controlled by a control grid, the transit time effect in the case of ultrashort waves causes an input resistance between grid and cathode that is equal to Kk ² ZS, where K is a tube constant, λ die. Wavelength and 5 "means the steepness of the cathode current. With a steepness of 7 to 10 mA / V, input resistances of up to 4 kΩ can be achieved with modern tubes Oscillator frequency is supplied, an electron flow to the first control grid, which also has a damping effect.

According to the invention, in order to increase the electronic input resistance, the area is ultra-short Waves correspondingly reduced the steepness associated with the control grid and cathode current, e.g. B. on a quarter, and then one becomes like this to compensate for the resulting loss of steepness large secondary emission multiplication of the electron flow controlled by the control grid by means of a multiplier plate applied that the amplifier tube with multiplication approximately the same Overall slope like a normal amplifier tube without multiplication.

A secondary emission multiplication of that coming from the cathode and controlled by a control grid Electron flow using a secondary emissive multiplier plate is for Increase in slope known. In the case of the tube according to the invention, on the other hand, the steepness should be opposite a normal tube without multiplication cannot be increased, since the invention is only a reduction of the electronic input resistance is intended.

The drawings show exemplary embodiments of the invention.

Fig. 1 shows a straight-ahead amplifier stage in which use is made of the secondary electron multiplication to increase the electronic input resistance between the control grid G ₁ and the cathode K. The cathode rod K is surrounded by the Wehnelt cylinder W _{z in} such a way that electrons can be easily bundled and emitted in only one direction. After passing through the control grid G _1, they hit a plate which is coated with a slightly secondary electron-donating layer and, by means of the voltage divider R ₁ , R _{2 parallel to the anode voltage source t / 6} , receives such a positive bias that optimal multiplication occurs . The secondary electrons are attracted by the anode A , which is at a higher positive potential, and flow through the working resistance R _a

Amplifier tube with high
electronic input resistance

Applicant:

Telefunken GmbH,
Berlin NW 87, Sickingenstr. 71

Johann Stegmüller, Ulm / Danube,
has been named as the inventor

away. Because the subsequent multiplication of the secondary electrons allows the primary component of the cathode current to be reduced to about a quarter, the electronic input resistance must be increased to four times that of the tubes currently in use, so that one can count on about 12 IcQ. It will also be possible, as shown in Fig. 1, to be able to dispense with an additional screen grid, since the Wehnelt cylinder and the multiplier plate 5 ^1, which is at ground potential in terms of alternating current, allow the control grid to be largely shielded from the anode. This has the further advantage that this tube has an inherent noise that corresponds to that of a triode with the primary slope. In this arrangement, if the capacitor C _{1 is} omitted, an amplified voltage in phase with the control voltage occurs at the resistor R _1. If the multiplier plate is therefore connected to the control grid via a capacitor, which is diverted via a resistor, breakover voltages can be generated in a simple manner by means of a single tube.

In Fig. 2, the same principle is used for a mixing tube that also works in the VHF area without any reaction. The primary system is the same as in Fig. 1 with the only difference that there is an additional screen grid G ₂ , which is at positive potential and fed via the filter element R _s , C ₂ , which is the control grid of the multiplier plate S, which here is the oscillator voltage is supplied, should shield. The multiplier plate S is at such a positive potential that the multiplication has not yet started strongly. The oscillator voltage shifts the operating point in a known manner in areas that emit secondary electrons and thus enables mixing. In Fig. 2 would be of the in this voltage range

709 697/343

possible self-excitation by means of an oscillator circuit located in the anode line (with capacitor C ₃ ) and a feedback coil located on the multiplier plate. The IF voltage will then build up on the IF circuit (with capacitor C _4). A reaction is impossible because no space charge forcing the electrons to reverse can occur after the screen grid.

Claims (4)

Patent claims: 1. \ ^r amplifier tube with high electronic input resistance for ultrashort waves, characterized in that the normal slope associated with the control grid and cathode current is reduced in accordance with the required high input resistance, e.g. B. to a quarter, and that in order to compensate for the resulting loss of steepness, a multiplier plate of the secondary emission multiplication of the electron flow controlled by the control grid is so large that the amplifier tube with multiplication has approximately the same overall slope as a normal amplifier tube without multiplication (Fig . 1 and 2). 2. flip-flop circuit using an amplifier tube according to claim 1, characterized in that a resistor (R ₁ ) lying in the feed line of the multiplier plate (S ) corresponding amplified alternating voltage with the same phase position as on the control grid (G ₁ ) is used to generate flip-flop frequencies is done by adding control grid and multiplier plate accordingly, e.g. B. are coupled to one another via a capacitor. 3. Mixing circuit using an amplifier tube according to claim 1, characterized in that the cathode current controlled by the control grid _{passes a screen grid (G 2} ) and finally impinges on a multiplier plate (S) in which the operating point is stored so that the secondary emission is not yet has fully started and a supplied oscillator voltage only shifts the operating point into strongly emitting areas for the purpose of mixing the _{input frequency at the control grid (G 1} ) with the oscillator frequency and decreasing the intermediate frequency at the anode (A) . 4. Mixing circuit according to claim 3, characterized in that at the specified operating point of the multiplier plate (S) a feedback from the oscillator circuit lying in the anode line to the feedback coil connected to the multiplier plate is exerted, which makes a separate oscillator tube superfluous (Fig. 2) . Considered publications:
U.S. Patent Nos. 1,903,569, 2,198,329;
Swiss patents No. 221 125,604 423; "Television and sound film", September 1939, pp. 65 to 68. Cited earlier rights:
German Patent No. 940418. 1 sheet of drawings © 709 597/343 9.57