A digital buffer is always made by two cascaded cmos inverters.
I can always see that a shunt feedback resistor is usually connect from the output of the first inverter to its input.
I want to know why the shunt resistor is used? What's its purpose?
it is used to prevent the occurence of metastable state in the inverters by the usage of feedback... also it increases the current sourcing ability of the buffer and decreasing the output impedance...