COMPRESSING CIRCUIT

摘要

PURPOSE:To prevent the input/output characteristic from being dispersed depending on the characteristic of components by using a characteristic of a linear operating region of a MOS transistor(TR) in place of a resistor having been in use for a conventional root compression circuit. CONSTITUTION:Since the drain and gate of the 1st N-channel MOS TR 11 are made short, the TR is operated in the saturation region and a current Iin flowing from an input terminal 13 to a terminal 15 is given by equation I, where Vth is a threshold voltage of the N-channel MOS TR 11, W1 is a channel width, L1 is the length of channel, K' is a gain coefficient and VCOM is a potential at an input terminal 16. On the other hand, let the input voltage of the circuit be Vin, the current Iin flowing from the input terminal 13 toward the terminal 15 is given by equation II since a MOS TR 22 is operated in a linear region. When a gate-source voltage Vgs is sufficiently larger than the drain-source voltage (Vin-VCOM), the equation II is approximated as equation II'. Since the relation of Iin=-Iout exists, equation III is introduced. Thus, the parameter K' depending on the process is erased.