We need to setup a 3 switch wherein if more than 2 switch are open, the LED will light. Materials should only be 2 transistor NPN and 2 PNP transistors, LED , resistors and wires. If switch is off it will generate negative volt, else, it will give +5 volts ( There is also a separate - and +5 volts source aside from the switches) (Switches are from the Digital trainer). It doesn't matter where LED will glow very bright, as long as there is a light on led, it counts as on.

Is it possible to make a circuits with only 2 NPN and 2 PNP transistors?

 

What have you been able to come up with on your own so far?

hgmjr

 

still unsuccessful. I made 3 AND gates and 1 OR gate (without doing the required limited transistors). But the output is wrong

 

Have you drawn up a truth table? It is then possible to make a network to match.

Can you use diodes, or are transistors it?

 

Here:

0 0 0 = 0
1 0 0 = 0
0 1 0 = 0
0 0 1 = 0
1 1 0 = 1
1 0 1 = 1
0 1 1 = 1
1 1 1 = 1

No diodes, just Transistors as a Basic ON and OFF switch (General Purpose Transistors)

 

Just a suggestion, whenever you make a logic diagram use a sequential count. Patterns show up better too.

0 0 0. 0
0 0 1. 0
0 1 0. 0
0 1 1. 1
1 0 0. 0
1 0 1. 1
1 1 0. 1
1 1 1. 1

Ever study how to build a Schmitt trigger using transistors? You may be able to set up a voltage comparator threshold using resistors and transistors.

 

I really can't see how this can be materialized. Give me 6 npn's and 4 pnp's and sure, I 'll do it, but with such a tight budget I'm at a loss.