The Meyer Lectures on Digital Systems
Module 1: Boolean Algebra & CMOS logic structures
© 2013
1.3 Properties of Open Drain NAND Gates
Introduction
Open-Drain (OD) NAND gates are an unusual sort of logic gates. Unlike a traditional logic gate containing both N-channel and P-channel MOSFETs, the OD NAND gates only contain N-channel MOSFETs which means it is only connected to ground. Thus an external power source of 5 volts is connected to the output with a pull-up resistor connecting the two.
OD NAND gates are different than ordinary NAND gates. They do not provide power and only provide a possible connection to ground, as mentioned above. The video below will enlighten this concept and explain how OD NAND gates operate.
It is important to know how to hook OD logic gates in a configuration known as 'wired logic'. I will show you how this hookup is actually the same as an AND gate in the video below. This equivalence can be utilized while making combinational circuits, which are digital circuits that only depend on its inputs (that is covered in Module 2).
Relevant Links
Back to table of content for "The Brown-Meyer Lectures on Digital Systems Design"
