SU1067538A1 - High-resistance resistor - Google Patents

Description

(Ls

X

05

SP

with

00

Rig.1 The invention relates to radio engineering and can be used in high-frequency electric circuits of amplifiers, power ramps, controlled and uncontrolled attenuators, and other devices. High resistance is known. a resistor containing a resistive element in the form of a rod, covering its full conductive cylinder, a common body, two iris diaphragms and ID fixing elements. The disadvantages of a high resistance resistor are the complexity of the design, large size. In addition, only the distribution capacitance of the resistive element per hollow cylinder is not sufficient to significantly expand the range of operating frequencies of the high-resistance resistor. The closest to the invention in technical essence and the achieved result is a high-resistance resistor containing a dielectric cylinder with a resistive element and an insulating coating successively applied to it, end contacts and a conductive element with a contact terminal placed on the insulating coating. In a known high resistance resistor, the conductive element is made in the form of a closed ring with a contact terminal, which is connected to one of the end pins 12. However, the conductive element increases the parasitic capacitance of the high resistor between the end pins. This leads to a limitation of the operating frequency range ... The purpose of the invention is to expand the range of operating frequencies. The goal is achieved by the fact that in a high-resistance resistor containing a dielectric rod with a resistive element sequentially applied to it and an insulating coating, face contact leads and a conductive element with a contact terminal, placed on the insulating coating, the conductive element is in the form of a spiral, Its fins are isolated from each other, and its contact output is connected by the outer end of the helix. FIG. 1 shows the construction of the high resistance resistor in FIG. 2 section A-A in FIG. one; in FIG. 3, the equivalent circuit of the high-resistance resistor (prototype); in fig. 4 is equivalent to the proposed high-resistance resistor; in fig. five ; and 6 - amplitude-frequency characteristics (AFC) of the resistor. The high-resistance resistor contains a dielectric rod 1 with a resistive element 2 applied to it, a coating 3, end leads 4 and 5, and a conductive element consisting of a conductive tape b and a dielectric tape 7 insulating the conductive coils from each other. The outer end of the conductive tape b of the helix is connected to the contact terminal 8, which, when using a high-resistance resistor in the radio engineering device, is connected to the common conductor, i.e. is grounded (in Fig. 1, common conductor. not shown). The operation of the resistor in the electrical circuit does not differ from the known ones, however, the range of its operating frequencies is much wider for the following reasons. The equivalent circuit (Fig. 3) of the high-resistance resistor (prototype) contains the distributed capacitance of the resistive element 2 (C); capacitance meukdu by end pins 4, 5 (C) 1 capacitance between conductive and resistive elements (. Ср); distributed capacitances between the common conductor (ground) and the resistive element 2 (C))} the resistive resistance of the high resistor ((). The capacitance Cc increases the total parasitic capacitance of the resistor, and the capacitance C is small and insignificantly affects its operating frequency range. that the frequency properties of the resistor are most significantly influenced by capacitance C, the equivalent circuit of the high-resistance resistor when grounding the contact output 8 of the conductive element (installed at equal distances from the end pins 4 and 5) can be shown as shown in Fig. 3. The conductive element combines the capacitance C formed by the first turn of the spiral b and the resistive element 2 (this capacitance is almost independent of the number of turns of the spiral) and the inductance formed by all the turns of the spiral B. the element divides the resistance of the high-resistance resistor in half, and its capacitance - with a certain coefficient m (i.e. C., / t). The impedance of the resistor at O is important. In this case, as 9 comes from formula (1), the constant time of the resistor can be reduced four times (almost 1.8-2 times). In the real case, the CQ capacity value cannot be large. Determine the value of this capacitance, at which the impedance of the high-resistance resistor is least dependent on the frequency. The function of the working attenuation of the resistor (Fig. 4) is determined by the ratio, - ° 4 2 "2 2 R A O 2 Z o 0 h and rf + v is the normalized frequency; w - circular frequency; resistance of the signal source and the load, between which the resistor is turned on From the formula (2) we find the optimal value of capacitance C, corresponding to the maximum flat response frequency of the high-resistance resistor Cpt ™ Taking into account that the distributed capacitance of the resistor is determined by the relation 0 | О C 0.0-f- iO p F / cm, (4) and the capacitance C with a small thickness of the insulating coating 3 can be determined by the formula of a flat capacitor 0, C GpF, then the ratio (3) connecting the size of the resistive element and the first turn of the helix 6 takes the form .e G. .. (b) ", 56 In ratios (4) - (6), the notation is accepted: E is the relative permittivity of the insulating coating of the resistor; O - the diameter of the dielectric cylinder with the thickness of the resistive element; 8 width of the ribbon conductor of the spiral 6; d is the mass of insulating coating 3; L is the length of the resistive element 2; kf is the shape factor of the resistor, equal L / lo for resistors with cylindrical resistive film material (for resistors with spiral cutting, Kf is a function of a / i, where a is the distance between adjacent turns, and a is the helix neck). At С J, Sopt (Fig: 2), it is easy to determine the upper limit frequency of the resistor (by the level of distortion of the AHCBD) Ago.In the prototype and 2jj / R. It follows from equation (7) that capacitance capacitance C can additionally expand the operating frequency range of the high-resistance resistor by a factor of 1.6. The operating frequency range of the high resistor is further expanded by making the helix-shaped conductive element having inductive resistance. The working attenuation value of the high multiresistor, taking into account C and L (Fig. 4), is of the form 2. |.: .. d. - active and reactive components of the impedance of the resistor (H / 2 and Fig. 4); - normalized frequency; - cutoff frequency of the resistor at Cj; itO, Uc 0; ,, g, g. full resistance of the conductor of the segmented element at high conductivity of the helix 6; e is the resonant frequency of I s from the conductive element (which is chosen 2–3 times greater than the cut-off frequency of the resistor at). The results (Fig. 5) of numerical calculation using relation (8) for different values of K show that the inductance of the helix b (at the optimum value of capacitance C) further extends the range of the working frequencies of the high-resistance resistor by 1.82 times. Compare, for example, the curves corresponding to and g 0.5, where Luo Further expansion of the operating frequency range of the high-resistance resistor is achieved by decreasing the conductivity (increasing resistance) of the conductive tape 6. This change in the parameter of the tape 6 reduces the quality factor of the own resonance of the conductive element.

Claims (1)

HIGH RESISTANCE RESISTOR, CO *? holding a dielectric rod with a resistive element and an insulating coating successively applied to it, end contact terminals and a conductive element with a contact terminal placed on an insulating coating, characterized in that, in order to expand the operating frequency range, the conductive element is made in the form of a spiral whose turns are isolated from each other, and its contact terminal is connected to the outer end of the spiral. SU, ... 1067538