Exponential Function Generator with Fourth-Order Approximation

The paper presents an original CMOS exponential function generator with improved accuracy. The area of application for CMOS exponential circuits is extremely large, including telecommunication field, medical structures and many analog signal processing blocks. The proposed design is based on a new approximation method for implementing the exponential function that allows a very important increasing of the circuit accuracy. Using a new forth-order approximation function, the original pseudo-exponential structure dynamic range will be more than 33dB, for an error less than 1dB. The circuit has a low-voltage operation and simulations match theoretical results. The circuit is designed for implementing in 0.35μm CMOS technology, being supplied at 3V . The architecture of the proposed exponential function generator allows implementing any continuous mathematical function, the resulted function synthesizer circuit being designed for a low-voltage operation.