A new CMOS pseudo approximation exponential function generator by modified particle swarm optimization algorithm

Wide Range High Precision CMOS Exponential Circuit Based on Linear Least Squares Approach

“…In addition, To prove the efficiency of the circuit, frequency response is provided. Since some reported works work in subthreshold region [10][11][12][13], and some others have complex structure [11], [15], [21], thus their bandwidth is limited, while in this work all of the transistors are biased in the saturation region. Frequency response of the EXPFG circuit in Fig.…”

“…The most important aspects of EXPFG circuits include output dynamic range, linearity of the output in dB, accuracy, power consumption, and area efficiency. In the following, the literature review verified that most of the above mentioned parameters have a trade off with each other, and then different design techniques have been presented [10][11][12][13][14][15][16][17][18][19][20][21] to satisfy the compromise between the characteristics.…”

“…Considering the mathematical techniques, three methods have been presented. The first group emphasizes on the use of expansion of the EXP functions using Taylor series [14], [15]. The main weakness of this method is given by the relatively small output dynamic range, because of neglecting superior-order terms in Taylor series.…”

“…The third group deals with presenting new approximations of function in a limited range [14], [15], [20], [21] in which each term of the approximated series is realized using a voltage-mode [14], [15] or current-mode [20] circuits. The method presented in [14], [15] use pseudo-exponential functions which result in simple realization of the circuits and relatively low power consumption, however the precision and dynamic range have been sacrificed. Higher-order terms proposed in [20] benefit from higher dynamic range in comparison with above mentioned methods, at the cost of complex implemented circuits and lack of area efficiency which leads to increasing in power dissipation.…”

“…Higher-order terms proposed in [20] benefit from higher dynamic range in comparison with above mentioned methods, at the cost of complex implemented circuits and lack of area efficiency which leads to increasing in power dissipation. Beside these classifications, designing the circuit with single power supply is preferred to those in dual mode; while the circuits reported in [7], [10], [13][14][15], [18], [19] require dual supply voltages. In conclusion, a circuit with wide dynamic range, high accuracy and low power consumption is expected as a further work.…”