Translinear sin(x)-circuit in MOS technology using the back gate

Though the MOS transistor is a four-terminal device, it is most often regarded as being a three-terminal device. Therefore, many possible MOS circuits are overlooked. In this paper, the four-terminal point of view is elaborated with respect to MOS weak inversion translinear circuits. It is shown that, by using the back gate, translinear networks can be derived which cannot be realized with bipolar transistors. These networks increase the possibilities offered by translinear technology. A sin(x)-circuit, which is one of the possible applications of the new network, was measured. The circuit can operate at supply voltages of less than 2 V and with a total bias current of only 14 nA.