Modeling of tunnel diode oscillators and their use for some low temperature investigations

Abstract

The simple method of modeling of tunnel diode (TD) oscillators’ work is described, and may be applied also to the other types of negative-differential conductance oscillators. In particular, the calculation of the harmonic oscillation amplitude is performed by the energy balance method, based on TD measured the current–voltage characteristic’ (I–V curve), using only one fitting parameter—the tunnel diode’s measured bias at which oscillations are quenched by means of which the oscillator’s effective total losses are determined also. The formula for calculation of the TD generator’s frequency is derived; it agrees with experiment and permits determination of its dependence on the radiotechnical scheme’s elements and TD I–V curve’s shape. The results of the calculation in comparison with the experiment are reported for the oscillators of various constructions operating at different conditions. For this, more attention is given to the constructive solutions applied in the low temperature experiments. Examples of the TD oscillators’ use in cryogenic techniques as well as in the superconducting detectors of particles and radiation are presented. The oscillators described generate, under the certain conditions, low-amplitude (<40 mV) sinusoidal signals with a highly stable frequency (not worse than ΔF/F=10−9/min at liquid-helium temperatures) and low intensity of higher harmonics in the soft mode. The power released is less than 10 μW and the measuring rf magnetic field’s amplitude at a sample, placed inside or near the oscillator coil, is less than 1 mOe. Using designed facilities we have already detected normal-to-superconducting phase transitions of tin grains with diameters of about 2 μm and phase transitions in micrometer thick and 20 μm2 high-Tc superconducting films.

Superconducting phase diagram and FFLO signature inλ-(BETS)2GaCl4Coniglio1, Winter2, Cho3 et al. 2011Phys. Rev. B854770View full textAdd to dashboardCite

“…To measure the in-plane penetration depth, we designed a Tunnel Diode Oscillator [27][28][29] shown in Fig. 1 and described in [30], to operate at 390 MHz with the sample contained in a 4-turn 0.5 mm diameter coil.…”

Negative hair-bundle stiffness betrays a mechanism for mechanical amplification by the hair cell

“…What is the utility of negative stiffness, of which we are aware of no previous demonstration in a biological system? Negative resistance, an electrical analog of negative stiffness that occurs in physical devices such as tunnel diodes, serves engineers in the design of electrical oscillators and amplifiers (29). The membrane voltage-current relations of neurons and other excitable cells also display negative resistance, which underlies these cells' ability to generate action potentials (reviewed in ref.…”

Newly-Proposed Methods for Early Detection of Incoming Earthquakes, Tsunamis & Tidal Motion

“…In other words, one of the relatively easier ways relates with the replacement of the normal-metallic coil by the superconductive one. This may improve the tunnel diode oscillator stability by at least 1-2 orders of magnitude [2]. The next improvement relates with the substitution of the tunnel diode by the superconductive S/I/S hetero-structure  as much more less-powered active element (compared to tunnel diodes) for the measuring oscillator of the SFCO absolute-position sensor, with a few orders of magnitude less steep of its I-V curve's negative differential resistance [16].…”

“…The next improvement relates with the substitution of the tunnel diode by the superconductive S/I/S hetero-structure  as much more less-powered active element (compared to tunnel diodes) for the measuring oscillator of the SFCO absolute-position sensor, with a few orders of magnitude less steep of its I-V curve's negative differential resistance [16]. This may raise the oscillator stability by another 2-3 orders of a value [2]. Even these two modernizations are enough in order to enhance the stability of the measuring and reference oscillators of such a technique (Fig.3) and hence, to increase the signal-to-noise ratio (sensitivity) of the SFCO technologybased seismic detectors -by at least 3-4 orders of a value.…”

“…Besides, due to flat shape, even a little shift of the position of a normal-conducting plate, placed near the coil, may www.intechopen.com lead to strong distortion of the field distribution around the coil. These features, and the stability of TD-oscillators (F stability 1-10Hz, F/F10  7 -10  6  depending on the model & temperature  see [2,[11][12]) enabled us to reach 6 orders relative resolution in SFCO technique [3][4], permitting to effectively use it in a basic research [5][6][7][8], as well as in some modern technical applications [9][10]. In the last case, frequency of the oscillator is mainly used as a testing parameter, and the measuring effect is determined by a distortion of the MHz-range testing field configuration near the coil face by the vibrating copper plate, leading to the magnetic inductance changes of the coil, with a resolution  1-10pH (depending on operation temperature of a technique), resulting in the changes of test oscillator frequency.…”