7447 IC Why we use 10k ohm resistors with the input voltages to the 7447 IC?

[burnishedcrystal]

Hi,

According to my knowledge, for inputs to the 7447 IC, the input current to the IC inputs should be zero.

WHy we use parallel 10k resistor with the supply voltage when giving inputs to the 7447 IC as in the figure below?






Thanks

 

[KlausST]

Hi,

this question comes so frequently.....the last I remeber was just a couple of days before.

Please do a search about:
* "pullup"
* "pulldown"
* "unused inputs"

If still a question remains, please fell free to ask a specific question.

Klaus

 

[Vbase]

10K is too high value for TTL pull down, it's a waste of components. This circuit wasn't designed by a competent engineer.

 

[Audioguru]

The 7447 is very old TTL logic that has a 1.6mA max input current that tries to pull an input to a logic high. The resistor to ground at an input to cause a logic low input is 500 ohms (not 10k ohms) but 250 ohms is better. If the IC is a 74LS47 then the resistor to ground can be as high as 2k or 4k ohms.