High-precision Amplifier Research Articles

Dual feedback based bipolar current source with high stability for driving voice coil motors in wide temperature ranges

Bipolar current sources with a stability better than 0.1% in the temperature range of -30 to +70 °C are demanded for driving voice coil motors applied in a new ultra-quiet satellite platform, but almost none of the existing designs satisfy the harsh requirements. This paper presents a possible solution, which is essentially a floating-load, bipolar current source circuit with a dual feedback path. The key circuit is a composite amplifier (co-amp) composed of a high precision amplifier for error correction and a high power amplifier for load driving. The first feedback path comprises a specially designed four-wire current-sense resistor for current-to-voltage conversion and a discrete instrumentation amplifier for amplifying the converted voltage and closing the loop. The second feedback path is a proposed compensation network for loop stability. Error budgets for evaluating current stability and choosing key components of the circuit are comprehensively studied based on a derived rigorous current equation. Loop-stability problems attributable to the inductive load and the high open-loop gain of the co-amp are analyzed, and the proposed dual feedback compensation method is verified by theory, simulation, and measurement. All these contributions are demonstrated by three implemented prototypes with an output of up to ±2A. The measured results agree well with theoretical predictions. The best and the worst stability performances of the three prototypes at +2 and -2A are, respectively, 394 and 986 ppm in the temperature range of -30 to +70 °C, which are close to the theoretical value of 776 ppm.

Improving the Characteristics of a High-Precision Measuring Amplifier by a Powerful Digital Signal Processing

The maximum resolution when measuring transducers, which operate on the strain gage principle, is physically limited. In addition to a very good analogue measurement technology, the quality of the measured signals can be further improved by a correct and powerful digital signal processing.The new amplifier QuantumX MX238B maintains the well-known and proven 225 Hz carrier frequency technology combined with the patented background-calibration function of the high-precision amplifier DMP41 and in addition with a powerful digital signal processing. This paper explains the digital signal processing and the achieved improvements.

High-precision amplifiers for strain gauge based transducers - first time realized in compact size

<p class="Abstract"><span lang="EN">In cases where accuracy matters, and in metrology of mechanical quantities such as force, torque or pressure this is definitely the case, are almost exclusively realized by transducers, which are based on strain gauges. To exploit the potential of the widely used high-precision static measurements the demands on </span><span lang="EN-GB">precision amplifiers steadily grow. This paper gives exact details to further progress of the precision amplifiers used and how compact they can be realized nowadays.</span></p>

The Design of Automatic System for the Calibration of Testing Temperature Cutter with Thin Film Thermocouple

In order to get an accurate online measurement for the transient cutting temperature in precision, in an ultra-precision cutting process,a temperature measuring device should be assessed whether it can obtain precise magnitude readings and variables of which are measured accurately. The just produced thin-film thermocouple used to measure tool cutting temperature must be correctly calibrated[3,4] , however traditional calibrating process problems rely on manual operation completely with lots of problems such as low efficiency, high labor intensity and large error. this paper proposes an automatic calibration system for thin-film thermocouple by using temperature measuring furnace, data acquisition card and computer-based software. The system makes an automatically and intelligently calibration process. By using a high-precision data acquisition card and precision amplifier circuit, eight thermocouples can be calibrated at the same time automatically which effectively shortens the calibration time and improves the accuracy. Use temperature metering furnace to control data acquisition. Secondary error from using standard thermocouple and other methods to collect the temperature metering furnace real-time temperature is eliminated. The system software modules consist of data reading, data processing, data display, database operation, data query and report generation module. The experimental results show that nonlinear fitting error is less than 0.6% within the temperature measurement range, which meets the requirement of the secondary precision of thermocouple error. This paper intends to provide a new calibration method for thermocouple temperature measurement tool development and production[7].

Advances in High-Precision Amplifiers—The Extra L Opposed Current Converter

In existing half/full-bridge high-precision amplifiers, output distortion is present due to the required switch blanking time. The OCC topology does not require this blanking time but has a much higher total inductor volume compared to the half bridge. In this paper, a patented new topology is introduced that has the advantages of the OCC but with a much lower total inductor volume. The basic operation and properties of the ELOCC topology are explained including an extended optimization of the total inductor volume and an average model for control design. A prototype ELOCC current amplifier has been developed. The behavior of this prototype is in good agreement with the obtained simulation results. Even though the prototype is not fully optimized, the linearity compared to a full bridge is already impressive.

Design of CMOS Amplifier Using New CCII Topologies

A high-precision amplifier design in a stander 0.35μm CMOS process was proposed. This design obtains a high-performance by proper application of dynamic element matching to a second generation current conveyor (CCII). In comparison with the traditional CMOS circuits, the proposed approach can not only increase the output swing and decrease output resistance but also compensate the effect of the input offset and 1/fnoise voltage. The simulation results show that the gain error is reduced 38~50 times than the traditional amplifier, and the precision is significantly improved. So the proposed circuit is suitable for the design of special amplifiers used in various detections and signal mediation.

A bridge for the comparison of resistance with capacitance at frequencies from 200 Hz to 2 kHz

A bridge for the comparison of resistance with capacitance has been designed and constructed. It is a six-arm generalization of the quad bridge and, while retaining the accuracy of a passive-component bridge, makes extensive use of high-precision amplifiers in both source and detector circuits. It will provide a link between the calculable capacitor and the ac quantum Hall resistance (QHR).

Time synchronized measurement of multi-bridge force transducers

This report describes the analysis and evaluation of a multi-bridge force transducer with a newly developed multi-channel amplifier system, which is able to measure the different individual strain gauge full bridges with up to eight high-precision amplifiers in an absolutely simultaneous way and with small measurement uncertainty. With the suitable evaluation software, it is then possible to calculate the sums and differences of the different output signals and with those, perform an analysis of the force transducer’s measurement behavior. It is also possible to gain results of the behavior of the materials testing machines in the presence of side forces, moments as well of swinging of the masses of dead weight force standard machines.

A unitary analysis of voltage mode and current feedback op-amp circuits

This paper presents a unitary analysis method for voltage mode (VM) and transimpedance-current feedback (CFB) op-amp circuits. This methods uses a unified model for both op-amps; thus it permits a direct comparison for the circuit parameters. The point of the presented method is the separation of the signal graph of the analyzed circuit in two different paths: one that controls the gain and another that determines the circuit bandwidth. Thus one obtains a direct sight on the circuit elements that control this parameters. We extend the analysis method on differential current feedback (DCFB) op-amps circuits. Symbols for CFB and DCFB were introduced to simplify the circuit descriptions. As an application we analyze some high precision and large bandwidth amplifiers.

Linear tunable resistance circuit using gallium arsenide MESFETs

Designs for linearised, linearly tunable grounded and floating resistance circuits using GaAs depletion-mode MESFETs are presented. Simulations confirm good linearity and admittance characteristics up to 10 GHz. Applications include tunable filters, oscillators and high-precision amplifier loads. >