Logarithmic transformation circuitry for use in semiconductor integrated circuit devices

摘要

A gain cell circuit includes a logarithmic transformation circuit. The logarithmic transformation circuit includes a pair of first and second transistors, each of which has first and second current carrying electrodes and a control electrode. The control electrodes of the first and second transistors are coupled to input terminals of the logarithmic transformation circuit. The logarithmic transformation circuit further includes third and fourth transistors coupled to the first and second transistors. The third and fourth transistors have control electrodes serving as output terminals of the logarithmic transformation circuit, first current carrying electrodes connected at first and second circuit nodes to the second current carrying electrodes of the first and second transistors, and second current carrying electrodes coupled to a power supply voltage. The logarithmic transformation circuit further includes an impedance element connected between the first and second nodes, and level-shift circuits connected to the second current carrying electrodes of the first and second transistors and to the control electrodes of the third and fourth transistors.