Hi. Please I need help with the output currents and voltages of logic gates. I only want to make a simple circuit in which a light is turned on depending on the state of 3 switches, but when reading more and more about logic gates more confused I am, and have not enough knowledge to understand the internals of a logic gate.
For instance according to the datasheet, my TI SN74LS08 (Positive AND Gate) can source up to 8mA when the output is low (0V) and sink 0,4mA when high (5V). So theoretically, if i want to turn on a LED with both inputs high, besides is not enough current, because the IC will sink current, the anode should go to Vcc and the cathode to the output pin, is this so?. And if needed, the transistor should be PNP, right?.
Well, testing with the breadbord in real life all is happening reversed (and what I think seems more logical). When both inputs are high the output is high (5V) and the LED is turned on, but only if the anode is connected to the output and the cathode to ground.
As you can see is such a huge mess for me. When and where is flowing the current?.
For instance according to the datasheet, my TI SN74LS08 (Positive AND Gate) can source up to 8mA when the output is low (0V) and sink 0,4mA when high (5V). So theoretically, if i want to turn on a LED with both inputs high, besides is not enough current, because the IC will sink current, the anode should go to Vcc and the cathode to the output pin, is this so?. And if needed, the transistor should be PNP, right?.
Well, testing with the breadbord in real life all is happening reversed (and what I think seems more logical). When both inputs are high the output is high (5V) and the LED is turned on, but only if the anode is connected to the output and the cathode to ground.
As you can see is such a huge mess for me. When and where is flowing the current?.