辅助数字电路课程学习，说明TTL电路中驱动电流之间的 关系。 -auxiliary digital circuit courses on TTL circuit-drive current relationship.

数字电路学习。TTL方向器的具体工作过程。各器件导通截至情况和电路各点电压变化。-digital circuit study. TTL direction for the specific work process. Conduction of the device and circuit as the voltage changes.