| 摘要 |
PROBLEM TO BE SOLVED: To provide an input buffer circuit, which is fitted to both a low voltage interface and a regular LVTTL interface and whose operation speed is high. SOLUTION: In an input buffer circuit, self-biasing voltage generated by a self-biased differential amplifying circuit 41 is used not only for tracking common mode input voltage but also for controlling the currents of a current sink sinking current from a current source supplying currents to the differential amplification circuit 41 and from the differential amplifier circuit 41. Thus, self-bias voltage is substantially maintained to be constant, and therefore a whole transformer conductance gain gm of the differential amplification circuit 41 substantially becomes constant in spite of the change of reference voltage inputted to the differential amplification circuit 41. Thus, low voltage interface characteristics are improved. The input buffer circuit is provided with a swing width control circuit 45, preventing the swing width of the output signal of the differential amplifier, circuit 41 from extending excessively, in response to the inversion signal of the output signal of the differential amplifier circuit 41. Thus, the skew is reduced, and the operation speed is improved. |
