# resistor used with 74AC14

#### threegold

Joined Jul 1, 2008
2
i have a circuit, the output of 74AC14 goes to CPLD.
do anyone know what is t
he purpose of 2.2k resistor here... pls view the attachment for circuit...

thanks alot

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#### mik3

Joined Feb 4, 2008
4,846
Maybe to protect from possible spikes.

#### Papabravo

Joined Feb 24, 2006
12,301
i have a circuit, the output of 74AC14 goes to CPLD.
do anyone know what is t
he purpose of 2.2k resistor here... pls view the attachment for circuit...

thanks alot
The resistor in conjunction with the input capacitance of the gate input forms a single pole low pass filter. It is also known as a damping resistor. Assuming an input capacitance of say 12 pf, the RC time constant of the LPF would be
Rich (BB code):
12 pf * 2200 = 26.4 nanoseconds