NOR=gate with conventional two parallel transistor input - has series diode and resistor preventing input transistors saturating, to reduce switching time

摘要

The NOR-gate consists of a conventional arrangement of two parallel input transistors (T1, T2) with shared emitter and collector resistors, and an output transistor (T3) coupled by its base to the collectors of the input transistors and with its emitter forming the output (A). A diode (D) is connected in series with a resistor (R4) across the shared collector resistor (Rc) and ensures that the input transistors do not saturate. The series resistor (R4) is one tenth of the collector resistor. This diode and resistor increase the steepness of the signal's edges and reduce switching times correspondingly.