Abstract
As single tunneling magnetoresistive (TMR) sensor performance in modern high-speed applications is limited by breakdown voltage and saturation of the sensitivity, for higher voltage applications (i.e., compatible to 1.8 V, 3.3 V or 5 V standards) practically only a series connection can be applied. Thus, in this study we focused on sensitivity, 3 dB bandwidth and sensitivity-bandwidth product (SBP) dependence on the DC bias voltage in single and series-connected TMR sensors. We show that, below breakdown voltage, the strong bias influence on sensitivity and the 3 dB frequency of a single sensor results in higher SBP than in a series connection. However, the sensitivity saturation limits the single sensor SBP which, under 1 V, reaches the same level of 2000 MHz∙V/T as in a series connection. Above the single sensor breakdown voltage, linear sensitivity dependence on the bias and the constant 3 dB bandwidth of the series connection enable increasing its SBP up to nearly 10,000 MHz∙V/T under 5 V. Thus, although by tuning bias voltage it is possible to control the sensitivity-bandwidth product, the choice between the single TMR sensor and the series connection is crucial for the optimal performance in the high frequency range.
Highlights
Since the demand for high-speed current-sensing systems is constantly growing, it is necessary to find new solutions for sensors which can provide the possibility of reliable current monitoring under different conditions
In this contribution, we have focused on the sensitivity, bandwidth and sensitivity–bandwidth product (SBP) dependence on the DC bias voltage in single and series-connected tunneling magnetoresistive (TMR) sensors
We show the nonlinear dependence of sensitivity and sensitivity-bandwidth product (SBP) on bias voltage in a single sensor, and their saturation below 1 V, and the linear sensitivity and SBP product increase with bias in the series-connected sensors
Summary
Since the demand for high-speed current-sensing systems is constantly growing, it is necessary to find new solutions for sensors which can provide the possibility of reliable current monitoring under different conditions. When applied in critical, high-speed electronic systems (e.g., power converters), accurate current monitoring, during different, fast changeable operation modes, is the crucial issue to ensure a high level of the system reliability and damage prevention [5,6] To fulfill these requirements, magnetoresistive (MR) sensors based on magnetic tunnel junctions (MTJ) can potentially be used, providing modification of the sensing properties such as sensitivity or linear range, tunability of the resistance and adjusting dynamic parameters, including frequency bandwidth, which can reach tens of MHz [7,8]. Establishing the bias voltage influence on the sensitivity and 3 dB bandwidth of CoFeB/MgO/CoFeB-based single and series-connected sensors becomes highly relevant for application in modern, high-speed electronics. We show the nonlinear dependence of sensitivity and SBP on bias voltage in a single sensor, and their saturation below 1 V, and the linear sensitivity and SBP product increase with bias in the series-connected sensors
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