Electronics > Beginners
Need help with a transistor and gate.
hhoka:
I made this circuit here: https://imgur.com/a/4Wr5zZs The problem is, that while A is at 0V, B is at 2.9V the output is high. I'm not sure why this is, and I've tried different resistors too (2k, 10k, 20k) but none of them worked. What's wrong here?
Damianos:
I am guessing that the output is around 2.5 V.
If we remove the upper transistor, then from input B to output there is a resistor and a diode (the BE junction of the lower transistor).
hhoka:
Yes, it's 2.5v. Why is the upper transistor acting like that?
Zero999:
--- Quote from: hhoka on February 16, 2019, 09:56:13 am ---Yes, it's 2.5v. Why is the upper transistor acting like that?
--- End quote ---
It's exactly what you should expect to happen.
The upper transistor is off and isn't doing anything. Current is flowing from pint B, through the transistor's base and appearing at the emitter.
hhoka:
How should I fix this to get the desired output? I read somewhere that this is an improper design of an AND gate, instead you should make a NAND and just invert the output, is this what I'm supposed to be doing?
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