Exponential and logarithmic functions using standard CMOS 0.8 μm technology

The main disadvantages of the analog design are the duration and the complexity of the design which involve high development cost and difficult modifications. An analog programmable network seems to be a solution for a rapid prototyping, a reduction of the duration of design and an economic production compared to the existing methods. Within the Laboratory of Image Signal Acoustic of the University of Chemistry Physic and Electronics of Lyon, work was undertaken for the development of an analog programmable cell. This cell fulfils the basic linear functions such as the addition, the subtraction, the multiplication and the division. However, in most applications, data processing is not linear. Thus, to extend the application range of this cell, the nonlinear functions logarithm and exponential are added. The exponential is realized by transistors operating in weak inversion region, the goal is to obtain the behavior of a bipolar transistor while remaining in standard CMOS technology