micro pic input

[jay543_uk]

This may be a stupid question but here goes, What is the smallest current required on a micro pic input pin for it to work. say i was using a 16f876a and had a 5v input from a transistor onto rb1, how much current would the pic be drawing on that pin??

The reason i ask is because iv been reading up on transistors and i have a few ideas on a circuit i would like to make, it would mean using a transistor in a common emitter format and from what i can see i need to no Ic current required to work out what resistors to set the bias ect.

Am i right in thinking that Rc resistor would also control the current on the output of the transistor

sorry if this is a stupid one but i had to ask.

jason

 

[vne147]

I don't know if there is a spec for that. The I/O pin senses applied voltage when set to high impedence (i.e. an input). The data sheet defines input leak current as 1µA so it's probably not higher than that if it's necessary at all.

 

[Nigel Goodwin]

It's a CMOS input, so requires VERY litle current - in fact so little that you should use pull-ups or pull-downs to stop it floating.