Direct, fast, and accurate measurement of VTand K of an MOS transistor using a VT-siftcircuit

Based on a V_T-sift circuit, a new characterization technique is presented with which the value of both K, the transconductance constant, and V_T, the device threshold voltage, of an MOS transistor can be measured directly, obtained from the drain current of the device to be tested and the voltage difference between the output and input nodes of the V _T-sift circuit, respectively. The proposed method has been verified experimentally and compared advantageously with the commonly used linear regression technique in transistor characterization and wafer manufacturing. An additional application field of the V _T-sift circuit is temperature compensation of analog circuits     

STM control of noninteger residual charge Q0 onthe central electrode of a double-tunnel junction

In a voltage-biased mesoscopic double-tunnel junction, the Coulomb threshold V_C is an e-periodic function of Q ₀, the charge on the inner electrode. In the STM work described here, a large Au tip images 100-Å Ag particles deposited on a cleaved BSCCO crystal substrate. Stable double junctions between the tip, the imaged particle, and the substrate are identified by Coulomb staircase I(V)'s. The control of Q ₀ is demonstrated by the variation of tip-particle spacing. The parameterization of such results permits a discussion of Q ₀ variation mechanisms     

An on-chip superconducting clock with two modes

A superconducting clock based on a 2-junction SQUID (superconducting quantum interference device) flip-flop with feedback is presented. The feedback consists of transmission lines that emanate from and return to the SQUID; the entire clock is built as a compact integrated circuit. The period of the clock is mainly determined by the length of transmission line, and there are two modes of operation that can be separately excited whose periods are in a ratio of 2:1. I-V data for a pair of clocks with different designed periods confirm the presence of the two modes, show how period depends on length, and give information on the switching time of the SQUID flip-flops. Specifically, the I-V data show that there exist both a fundamental model for flux bias at odd multiples of Φ ₀/2 (half-flux quantum) and a doubled mode with precisely half the period flux bias at even multiples. Clocks with longer transmission lines have longer periods, but simple scaling does not occur due to other sources of time delay     

A 300-A delta VF tester

The design and development of a relatively low-cost, high-current, transient thermal resistance tester are described. The tester, which employs delta techniques, was initially used to measure the die bond integrity of large power handling rectifier assemblies, but because of its versatility it can thermally characterize most semiconductor junctions. Circuit design details and testing of several products are illustrated, including the delta V_F and V _F measurements of power rectifiers and smart power ICs     

New improved bipolar and bilateral voltage to current converters

Some improved bipolar, bilateral voltage-source-to-current-signal converter schemes, using operational amplifiers (OA) as active devices, are described. Some of them are derived from an earlier scheme that uses the OAs in summing mode, and the others are derived from the conventional technique of using the OAs in current output configurations. Except for one scheme that uses a single OA for the realization, the others have ideal voltage-to-current transfer ratio and characteristics. The realization constraints in each case have considerable degrees of flexibility, and there is no effect of load variation as long as the OAs used in the schemes are not saturated due to increased input conditions. The admittance matrices, constraints of realizations, and sensitivity to passive parameters for the different schemes are tabulated for ready reference. It is shown that the schemes can be used as V-I and I-V converters with scaling facility of the conversion factors     

Analog-to-analog conversion with high normal mode rejection ratiofor power-line-frequency noise

A simple method that ensures high normal mode rejection ratio (NMRR) for power-line-frequency noise in dual-slope integration and voltage-to-frequency (V-F)-based A/D converters is proposed. Experimental results for normal mode rejection ratios above 90 dB achieved in an instrument designed with implementation of this method are also reported     

Widely extended new method for measuring the impedance (CxRx) at high frequencies withapplications

A method is described for the accurate measurement of the equivalent parallel capacitance C_x and resistance R_x of very high loss materials at high frequencies. The important characteristic of the method is its capability of measuring the value of C_x extending from 10^-2 to 10⁶ pF and R_x from 10 to 100×10⁶ Ω. The authors measure the humidity of tea leaves and rockwool by measuring the capacitance C_x of specimens irrespective of the value of R_x     

Digital correction of A/D conversion error due to multiplexingdelay

A measurement channel which consists of a multiplexer, sample-and-hold circuit, and analog-to-digital (A/D) converter is studied. It is designed for the synchronous sampling and measurement of two or more voltage signals V₁(t), V ₂(t), . . ., but the finite time of A/D conversion (ΔT) makes it impossible to acquire consecutive samples closer in time than ΔT. This can become a source of measurement error if further processing of the measurement data is based on the assumption of ideal synchronism. It has been found that interpolation filters, developed from the Lagrange polynomial interpolation, are useful tools for solving the problem of correction. An illustrative example of their use is presented     

An algebraic method to reconstruct the relative phases andpolarization of a complex vector in N dimensions based on3(N-1) amplitude measurements

A real vector X in n dimensions whose components are sinusoidally varying with time can be represented by an n-dimensional complex factor Ze^jωt whose real part is X. In different real coordinate systems, the components of X transform linearly, but the amplitudes of the components of Z transform nonlinearly. The author describes a method to reconstruct the relative phases of the (complex) components of Z (and, therefore, of X) based on the amplitude measurements of its n components in an orthogonal coordinate system and at least 2n-3 additional amplitude measurements in different directions. The author shows the necessary and sufficient condition on these additional directions to ensure uniqueness of the phase and polarization reconstruction for any arbitrary vector X, and presents an algebraic method for the reconstruction which offers substantial reduction in computing time over the method of reconstruction by nonlinear optimization. The result of this phase of reconstruction is the complete characterization of the polarization of X except for chirality     

An integration-type high-speed analog-to-digital converter

An analog-to-digital (A/D) converter consisting of a switched-capacitor integrator, comparator, and control circuit is presented. The conversion process consists of voltage-to-frequency (V/F) conversion to determine the upper M bits of an N-bit representation of an analog input voltage and the subsequent voltage-to-time (V/T) conversion to determine the remaining lower N -M bits. The total clock cycle required for N-bit resolution is 2^M+2^N-M at most. The circuits for the V/F and V/T conversion share most of the components and thus the converter can be implemented with the minimum component count. Error analysis shows that a conversion accuracy higher than 12 bits can be expected from its CMOS monolithic realization. Prototype converters built using discrete components have confirmed the principles of operation     

Common mode rejection ratio for cascaded differential amplifierstages

A simple equation for calculating the total common mode rejection ratio, CMRR_T, for cascaded differential amplifier stages is given, and it is applied to several typical cases in instrumentation circuits. Two factors for each stage, C and D, are defined, and it is shown that, in general, CMRR_T can be calculated by adding the reciprocals of the equivalent CMRR for each stage, which is defined as the product of its C factor and the product of D factors for the preceding stages. The acceptability of the approximate formulas is verified, and application examples based on typical situations in instrumentation circuits are given. It is shown that the assumptions made to obtain such a simplified equation are acceptable     

Towards a frequency measurement of the Rydberg constant using the 2S-8S and 2S-8D transitions ofhydrogen

A very precise measurement of the Rydberg constant is performed using a direct-frequency comparison of the 2S-8S and 2 S-8D two-photon transitions in atomic hydrogen with the difference of two optical standards connected to a frequency chain     

Computer-aided measurement of Q-factor with application toquasi-optical open resonators

A technique for automated measurement of Q based on the observation of resonator response at a set of points near resonance is presented. The resonance curve, suitably corrected for noise and the presence of unwanted modes, is transformed into a linear graph. On the basis of this transformation, an analysis of error in the measurement of Q is carried out. An example of measurement on an open resonator at 97 GHz, with an accuracy of about 1% in the evaluation of Q is included     

Effect of the n value and the field inhomogeneity on thequench current of superconducting cables [magnet winding]

A model developed to obtain a relation connecting the critical current and the quench current of superconducting (S/C) cables is described. The model is based on the hypothesis that the heat produced inside the cable is only due to the ohmic dissipation, and it is only removed by thermal exchange with the liquid helium bath. The ohmic dissipation is calculated by supposing that the electrical resistance of the S/C cable at the transition to normal state is: Rαlⁿ where l is the current and n (n value) is an integer number. To calculate the function R(I), the field inhomogeneity at the conductor due to the self-field is taken into account, introducing the effective critical field     

The study of transient electromagnetic fields in a multi-turn,voltage-excited laminated core reactor

A combined explicit and implicit finite-different scheme is used for analyzing transient electromagnetic fields in a multiturn, voltage-excited reactor with a laminated core of nonlinear magnetic property. In the analysis, the reactor is divided into iron, air and winding regions. By applying a step function and a time-variant sinusoidal voltage source, the time-dependent magnetic vector potential function is obtained with the aid of B-μ table. The transient responses of the current and inductance are given. The computed results are compared with those of an ideal R-L circuit, and an excellent agreement between the light-load result and the ideal value is found. The nonlinear effects on currents, flux distributions, inductances, and magnetic vector potentials due to the saturated iron core can be found in a heavy load condition     

High coercivity in melt-spun SmFe10(Ti,M)2 ribbons (M=V/Cr/Mn/Mo)

Magnetic properties of SmFe₁₀(Ti,M)₂ melt-spun ribbons were studied, where M is V, Cr, Mn, and Mo. The ribbons (M=V/Cr/Mo) quenched at 20 m/s exhibit the high coercivities of 4.2-5.5 kOe. Annealing the ribbons quenched at 40 m/s enhances their coercivities in the range of 5.9-10.0 kOe. In particular, SmFe₁₀ (TiV) and SmFe₁₀(TiCr) ribbons yield coercivities of 10.0 kOe and 7.9 kOe, respectively. This is the highest value among the reported melt-spun ThMn₁₂-type structure ribbons. The importance of Sm atmosphere during annealing in minimizing the Sm evaporation from ribbons is also demonstrated     

High density magneto-optical recording using 0.67 μm band highpower laser diode

High-density optical recording on a magnetooptical disk has been achieved by a compact optical head that uses a 0.67-μm-band high-power visible-light laser diode. The recording density has been improved to 1.5 times that for conventional optical recording, using a 0.83-μm laser diode, as a result of the increase in linear density and track density. The C/N ratio for the readout signal is greater than 50 dB     

A circuit approach to field computation

Many design objectives can be expressed more directly in terms of circuit parameters, such as capacitance and inductance, than in terms of the field vectors E and B. A simple, although radical, change is suggested to provide a closer link between the field and circuit views. The electric potential φ and magnetic vector A are defined, in energy terms, as the primary field quantities, and they are visualized as measures of the capacitance and inductance, respectively. E and B become auxiliary symbols denoting derivatives, so that the customary roles of the potentials and field vectors are reversed. Some of the practical advantages of the change are examined and are illustrated by example     

The segmented chirp Z-transform and its application inspectrum analysis

The chirp Z-transform (CZT) algorithm is known to be more flexible than the fast Fourier transform in calculating the frequency spectrum. However, its mathematical implementation is complex, and additional memory space is required. A modified CZT algorithm called the segmented chirp Z transform (SCZT) is introduced. SCZT has the ability to handle a very large amount of input data with very limited memory space and to limit its calculation to a portion of the frequency spectrum of interest with greatly increased dynamic range and frequency resolution     

A resonant bridge with frequency-dependent negative resistance

Investigations were conducted on the properties of 24 circuits for which the impedance in the ideal case is equal to s² E, where s is the complex frequency and E is a constant. For harmonic excitation each circuit forms a negative resistance-ω²E and is hence called a frequency-dependent negative resistance (FDNR). From these 24 circuits, four that are stable were selected; measurements were made on these, and their equivalent circuit diagrams were determined. A resonant bridge was constructed with one branch containing an FDNR. Using this bridge it is possible to measure inductances with dissipation factors, tan δ, as high as 10⁴