Experimental evaluation of computer-controlled variable gain analog amplifiers

摘要

Analog amplifiers are used as front-end electronics to pre-condition signals or for control applications where low latency matters. Highly dynamic systems such as adaptive analog filters or simulation of dynamic virtual environments in haptic systems, require amplification gain adjustment which can be digitally implemented. In this article, we will present and experimentally evaluate five digitally controlled variable gain analog amplifiers which use dedicated components, including multiplier amplifier, voltage controlled amplifier and digital potentiometer, or use low-cost JFET-based alternatives. The amplifiers are designed for the high amplitude, low frequency signals often found in control systems. A method of interfacing the amplifiers with a desktop computer is discussed. The performance of these amplifiers are compared for their gain linearity, zero command gain, gain symmetry, DC offset, bandwidth, and noise. While each amplifier displayed strength in some aspects, the best performing amplifier had a maximum gain error of 0.043 %, a symmetry error of 0.42 % and a DC offset of 0.026 V. Recommendations for the use of each amplifier are provided.