Abstract: A semiconductor memory device includes a memory part which stores data, a decoder which decodes a command externally supplied to the semiconductor memory device, and a precharge protection circuit which dynamically determines, based on the command decoded by the decoder, a period necessary to precharge a predetermined circuit part of the semiconductor memory device, so that a precharge operation on the predetermined circuit part can be protected.

Abstract: A bipolar transistor, connected between a high voltage source and a low voltage source, has a base connected to an input terminal. A clamp circuit is connected between the high voltage source and the base of the transistor. A first resistor is connected in parallel with the clamp circuit. An output terminal is connected to the emitter of the bipolar transistor. In one embodiment, the clamp circuit is formed by two diodes connected in series. In another embodiment, a second resistor for limiting current is provided between the input terminal and the base of the transistor. In yet another embodiment, the resistance value of the first resistor is smaller than the ON resistance of a pMOS transistor in the output circuit of a CMOS circuit connected to the input terminal. A high level from the output terminal produces a high level ECL level output with a potential that depends on V.sub.BE of the bipolar transistor, while a low level output depends on the level of the clamp circuit.