Quicj Question - Current Limiting on Logic-Logic lines

Other Hardware General Electronics
1

Hi,
I assume that AVR, 74000 series and 4000 series ICs all have high impedance inputs and so there is no need of current limiting resistors when making logic connections between devices in these families ?

And that this also holds for cross family connections i.e. AVR->74000->4000->AVR etc (assuming common supply)

Thanks

Duane B

2

There wouldn't be any need unless the wires in between would be in an enviroment where they may get accidently shorted, in that case a 220 ohm resistor wouldn't hurt on the arduino side to protect them from burning out

3

I assume that AVR, 74000 series and 4000 series ICs all have high impedance inputs and so there is no need of current limiting resistors when making logic connections between devices in these families ?

That is generally true as long as all the different chips you are working with are powered at the same Vcc voltage. Some of the CMOS logic chips can utilize higher and lower Vcc voltages then the older standard 74xx TTL chips.

Lefty

4

Thanks both

Duane B