Proposal of circuit configuration to reduce power supply voltage and circuit scale for CMOS exponentiation conversion IC utilizing weak inversion operation

Abstract

We proposed elemental technique for reducing power supply voltage and circuit scale for CMOS exponentiation conversion IC utilizing weak inversion operation to mount it on microcomputer chip. This IC implements to change the power exponent to any value by amplifying with adjusting gain after converting signal logarithmically, and finally converting it exponentially. We showed that the circuit scale can be reduced to several tenth times in order to generate a weak inversion current by cascading multiple stages of current-dividing current mirror circuits. Due to this current mirror circuit, circuit scale was reduced to 34.4%. We also proposed an exponential converting circuit that can halve the input voltage by using one pair of weak inversion MOSFETs. However, the proposed control method of the exponential value by utilizing the substrate effect was found to have about 8% of narrow control range. Although measured result shows that this IC does exponentiation conversion, power exponent value was 56% smaller than simulation result.