| 摘要 |
PURPOSE:To prevent the generation of current noise in other output signal in the simultaneous changeover of a bus signal or the like by adopting the push-pull constitution comprising two N-channel MOS TRs for the final stage TRs of an output buffer and generating a high level of a pre-stage circuit driving the gate of the power supply side MOS TRs from other power supply. CONSTITUTION:The two N-channel output buffer TRs 2, 3, are connected in series to form push-pull constitution and a connecting point between the source and drain is used as an output. The drain of the TR 2 is connected to a power supply VDD2 and the inverter 4 of the pre-stage is fed from the power supply VDD1. The same waveform is inputted to lots of bus inputs A1-An and outputs B1-Bn are driven simultaneously, then current noise is invaded in power supplies DD2 and SS in the inside of a semiconductor, but the noise of the power supply DD1 of the inverter 4 is very small. Thus, control pulses C1, C2 are brought normally into a high level and the signals C1, C2 go to a low pulse, then the time phase between both the switching is not overlapped at the simultaneous changeover of the buses thereby preventing no current noise to the outputs D1, D2. |
