A high-current very wide-band transconductance amplifier

A novel design approach for a high-current, very-wide-band transconductance amplifier is described. The approach is based on paralleling the input and output of complementary unipolar current-mirror cells. Each cell has a fixed current gain determined by the ratio of two resistors. A differential input voltage-to-current circuit drives the cell array. The design avoids the need for a single low-resistance current-sensing resistor and the attendant problems inherent in such resistors. Although the concept is still under development, a prototype of the cell-based transconductance amplifier was implemented with ten positive and ten negative current cells to gain some experimental familiarity with the approach in addition to providing verification of computer simulation results. The prototype transconductance amplifier is DC coupled, has a 3-dB bandwidth of about 750 kHz, and can deliver up to 35 A RMS (root mean square) at 100 kHz with an output compliance voltage of 5 V RMS. Other important characteristics such as output-load regulation and DC offsets are discussed     

A linear operational transconductance amplifier for instrumentationapplications

A linear operational transconductance amplifier (OTA) is described that consists of a linear transconductor and a translinear current gain cell followed by three current mirrors. The proposed circuit has superior linearity and temperature characteristic when compared with the commercially available OTA. A prototype circuit with a transconductance of 50 μS has been built with discrete bipolar transistors producing a linearity error of less than ±20% over an input voltage range from -0.8 to 0.8 V. The prototype OTA circuit also exhibits a transconductance that is linearly dependent on a bias current varying over four decades with a sensitivity of 1 S/A     

Calculated frequency characteristic of GR1482 inductance standardsbetween 100 Hz and 100 kHz

The Physikalisch-Technische Bundesansalt (PTB) calibrates inductance standards in the frequency range from 100 Hz to 100 kHz and beyond. The relative uncertainties achieved range from less than 5×10^-5 to 5×10^-4 (2σ) depending on the frequency and the value of the standards. Because of the strong frequency dependence of the inductance standards it is of interest to use a suitable equivalent circuit to calculate the most accurate approximation for the frequency variation. A model is presented which allows the values of a GR1482 inductance standard to be calculated over the whole frequency range from 100 Hz to 100 kHz within the measurement uncertainties     

20～100kHz铁基微晶电感材料Fe—Co—Si—B—C的研究

研究了合金元素对恒导磁微晶合金 Fe_(71)Co_7Si_9B_(13)的高频损耗及恒导磁特性的影响。发现碳(C)的加入能大大降低该合金的高频损耗。随着 C 含量的增加,高频损耗 P_(2/20k)单调下降,当 C 含量大于4(at)%后,P_(2/20k)不再随着 C 含量的增加而降低。该合金的等温 P_(2/20k～t_a)曲线(t_a 为保温时间)呈“U”型,属典型的微晶化效应降低损耗方式。x 射线衍射结果证明该合金的组织为 bcc 结构的α-Fe。认为 C 对损耗的影响机制不同于普通晶态合金中的李希特(Richter)效应。C 是易偏析元素,在微晶化热处理时,碳的偏析为细小α-Fe 的形成,提供了大量晶核,使合金的组织细化,从而细化了磁畴,降低了异常涡流损耗,使高频损耗降低并具有较高的动态导磁率。横向磁场热处理后该合金可成为优良的恒导磁电感材料     

Automatic inductive voltage divider bridge for operation from 10 Hzto 100 kHz

A bridge to calibrate programmable and manual inductive voltage dividers is described. The bridge is based on a programmable 30-b binary inductive voltage divider with terminal linearity of ±0.1 ppm in phase and ±2 ppm quadrature at 400 Hz. Measurements of programmable test dividers can be automated using software developed to align the bridge components and perform an automatic balance     

A Brightness Amplifier on Manganese Atom Transitions with a Pulse Repetition Frequency of up to 100 kHz

Technical Physics Letters - Results of the development and study of an image brightness amplifier on manganese atom transitions for problems of object visualization in active optical systems are...     

Extension of the NIST AC-DC Difference Calibration Service for Current to 100 kHz

The NIST calibration service for ac-dc difference of thermal current converters relies on multijunction thermal converters as the primary standards, and various thermal converters and thermoelements (TEs) as the reference and working standards. Calibrations are performed by comparing the ac-dc difference of a customer’s thermal current converter to the ac-dc difference of a NIST standard current converter. Typical artifacts accepted for calibration include single-junction thermoelements, multijunction thermal converters, and transfer shunts for use with TEs. This paper describes the standards on which the calibration service is based and the results of the study to characterize the NIST standards over the extended frequency range from 50 kHz to 100 kHz at currents from 1 mA to 20 A. The general method for the frequency extension at high frequency involves the use of thermoelements in the 5 mA range, with small frequency dependence, as the starting point for build-up and build-down chains to cover the whole range from 1 mA to 20 A.     

Chopper-stabilized operational transconductance amplifiers

A technique for chopper-stabilizing commercial linearized operational transconductance amplifiers (OTAs) to remove output offset current errors is described. Design equations which illustrate performance tradeoffs as a function of component values are given. The results are verified experimentally using a common bipolar OTA     

A spectroscopic study into the decomposition process of titanium isopropoxide in the nitrogen-hydrogen 100 kHz low-pressure plasma

Optical emission spectroscopy was employed for the study of the nitrogen-hydrogen and nitrogen-hydrogen-titanium (IV) isopropoxide mixtures in the 100 kHz low pressure capacitively coupled discharge. High-energy species were identified in the plasma phase. The behavior of the excited species versus the gas composition has also been investigated. The optical actinometry technique was applied in order to evaluate the N₂, CH, CO, CN, N, C and the H relative concentrations versus the hydrogen concentration in reactive mixtures. The effect of the hydrogen concentration in the nitrogen-hydrogen mixture on the decomposition processes of titanium isopropoxide was investigated. The plasma temperature (the H excitation temperature, the CN, N₂ and N₂⁺ vibrational temperatures and the N₂⁺ rotational temperature) as well as the electron number density were determined here. The temperature magnitudes (T_exc≈5700-7400 K, T_vib(CN)≈4700-8100 K, T_vib(N₂)≈2700-3050 K, T_vib(N₂⁺)≈1500-1600 K and T_rot(N₂⁺)≈660-890 K) indicated a very significant deviation from the LTE state.     

Optical emission spectroscopy study for nitrogen-acetylene-argon and nitrogen-acetylene-helium 100 kHz and dc discharges

The optical emission spectroscopy was applied to investigate the middle frequency (100 kHz) and dc low pressure discharges, generated in the nitrogen-acetylene-argon and nitrogen-acetylene-helium mixtures, commonly used for deposits of carbon nitride thin layers. Changes in the emission intensities of the selected species: CN, CH, C, H, N₂, N₂⁺ as well as Ar, Ar⁺ and He, were studied as a function of the discharge current. Excitation processes occurring in the presence of argon and helium were compared and discussed. The N₂-C₂H₂-Ar and N₂-C₂H₂-He plasmas generated in the 100 kHz and dc glow discharges were characterized by the excitation (Ar, He, H), vibrational (CN, N₂) and rotational (CN, N₂⁺) temperatures. A significant deviation from the equilibrium state was observed for the plasma containing argon as well as helium.     

A simple apparatus to plot the variations of the dielectricpermittivity versus temperature in the range of frequencies 10 Hz-100kHz

An apparatus able to plot the variations of the real and imaginary parts of the dielectric permittivity of materials versus temperature in the range of frequencies from 10 Hz to 100 kHz is presented. The circuit is based on a simple operational amplifier followed by detection, low-pass filters, and amplifiers. The resulting two DC voltages, which are proportional to ϵ' and ϵ", are sent to a plotter whose x input is driven by the temperature of the sampled     

Development of a compact efficient 10 Hz 20 TW Ti:sapphire laser system with a 1 kHz regenerative amplifier

We have constructed a compact efficient Ti:sapphire laser system that generates 30 fs, 630 mJ pulses at a repetition rate of 10 Hz. A new geometry for a single-stage multipass power amplifier is proposed that greatly weakens and even makes use of thermal lensing. Such geometry can realize high output in a single-stage power amplifier; otherwise at least two-stage power amplifiers are required. The new configuration simplifies the laser system and reduces the cost. The key point in this design is that the beam spot size evolution is considered in combination with the pulse amplification.     

A magnetic sense amplifier

A new mode of operation of a balanced magnetic circuit is described. With this new mode of operation, which utilizes pulsed current excitation, the detection sensitivity of the magnetic modulator circuit is combined with the high-speed amplification of parametric buildup. This combination permits detection of low-level current pulses applied during a specified time interval of the excitation sequence and provides subsequent amplification of the detected signal. Matched square-loop toroids are used. Signal currents which are a small fraction of the coercive MMF have been successfully detected. The limit of detection sensitivity depends upon the matching of the two cores. The parametric buildup has been made to occur for pump cycle times of 30 μs to 120 μs, depending upon the magnetic material used. The signal information is retained when the pulse excitation sequence is interrupted during buildup because the signal information is stored as a flux unbalance in the two cores during the time interval between excitation pulses. The use of this circuit mode as a sense amplifier for the detection and amplification of sense winding currents in magnetic memories is suggested.     

A Frequency Synthesizer for 10/2? kHz

A sinusoidal voltage source of frequency nominally 10/2? kHz (? = 104 rad/s) is derived from a 5-MHz standard. Digital counters are used to generate the required frequency, which differs from 10/2? kHz by less than 2 parts in 108, and is as stable as the standard. Using a crystal filter and low-distortion amplifiers, an output of 10 V rms with total harmonic distortion less than 1 part in 103 is obtained.     

Direct airborne acoustic wave modulation of Fabry-Perot fiber laser (FPFL) over 100 kHz of operating bandwidth

The idea of applying a simple Fabry-Perot fiber laser (FPFL) set-up in a free-running condition as an acoustic sensing medium is proposed. Conventional optical microphone requires a stringently aligned diaphragm to mediate the acoustic impedance mismatch between air and silica fiber. Motivated by the difficulty of optical sensing of airborne acoustic waves, a new sensing method is proposed to sense acoustic waves without the assistance of a diaphragm as transducer. By studying the output power fluctuation of the FPFL, the operating bandwidth and sensitivity of the proposed sensing method are determined. The tunability of the resonant frequency from 5 kHz to 85 kHz allows sensing of acoustic waves in the range of 100 Hz to 100 kHz. Tuning of the resonant frequency can be performed by changing the optical pumping power from as low as 10 mW to 68.5 mW or higher.