That will not work. If you think of the transistors as switches, and both inputs are high so both transistors are on, then they are trying to create a dead short across the battery. Depending on the condition of the battery, this may or may not destroy one or both of the transistors, but the circuit will not function correctly.The collector of the first transistor is directly connected to the 9V.
See circuit below.AND gate if you watch the LED, but like a NAND gate if you look at the output voltage.
why is it not a valid way to test it? and how should the schematic look like if i use another transistor?Because the circuit with R4 and LED on the right is not a valid way to test the voltage on the collector. Use a volt meter instead.
Or use another NPN transistor as an LED driver feeding off the NAND gate collector.
I think TS is confused between AND gate output voltage and LED being turned on when the output voltage is low.Also, if i remove R4 the LED on the right goes off if i push the buttons.
why is it not a valid way to test it? and how should the schematic look like if i use another transistor?
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