[SOLVED] IC Input and Output Currents

[arjob]

Hello guys, I am new to electronics. While i was experimenting with 74LS series ICs, I saw the peculiarity, that the I/O current does not match the specifications for the IC. For example the 74LS00 IC specification says, that its Output High current is -400 micrcoA, But I am getting close to 170 miliA. What the **** is happening!! How to measure these Output current properly..

If you do not understand the question pls ask.

 

[FoxyRick]

Current is generally drawn through an IC by a load. The current stated on such datasheets is generally the maximum that can be safely allowed through the device, not what they will provide as such. The IC output provides a voltage.

The load determines how much current will be drawn, in conjunction with the output voltage, and can be calculated by Ohm's law.

How are you measuring the current? I guess you are connecting an ammeter from the output to ground? If so, then you are short-circuiting the output and will eventually damage the device.

You can measure the output voltage like that, with the multimeter set to a voltage range.

Current is measured by putting the ammeter (multimeter in current mode) in series with a load. An ammeter has almost no resistance (otherwise it would effect the current it is trying to measure) so must not be connected simply between a voltage source and ground, without a load present - it will cause a short-circuit.

 

[arjob]

thanks so much. you made it clear enough!