A Quantum Well Hall Effect linear isolator with wide frequency response and low gain temperature coefficient

Abstract

A linear galvanic isolator was developed, using a compact and high sensitivity Quantum Well Hall Effect (QWHE) sensor. This sensor is based on a GaAs-InGaAs-AlGaAs heterostructure, with a maximum capacitance of 5.5pF and a 3dB bandwidth of 40.2MHz. As part of this work, a printed transmitter coil was also designed as part of this QWHE galvanic isolator. A linear relationship between input current and output voltage, at each frequency of the isolation device, were observed (R2≈1.0). The relative errors of frequency response between 0 and 100kHz were ≤5.4%. Two gain temperature coefficients were also obtained at low and high temperatures, α1 and α2, with a temperature of 280K being the boundary between the two regions. The mean values of α1 and α2 were (7.09±0.27)×10−4K−1 and (3.22±0.17)×10−4K−1 respectively. The controlling mechanisms for the amplitudes of α1 and α2 are suggested to be due to the temperature variation of the two-dimensional electron gas (2DEG) electron mobility, arising from the heterostructure nature of the QWHE sensor used. The QWHE isolator has high accuracy, large bandwidth, high frequency-gain linearity and thermal stability. Compared with commercial optical isolators, Silicon Hall sensor-based isolators and coil isolators, this QWHE isolator does not require any external light sensor transistor or ferrite toroid to enhance its sensitivity. As such, it is not affected by any nonlinear transistor behaviour, B-H curve or magnetic retention. The results indicate that this high sensitivity, highly linear QWHE isolator is suitable for use as a low cost, high efficiency, linear galvanic isolation device.