I'm pretty new to the hardware side of electronics and am building some basic logic gates. The first Im trying is an AND gate and the problem I'm having is that whenever I power the base of the transistor it's emitting power even with no power going through the collector. Any ideas as to why? Thanks. (Am using a BC475 transistor)

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    \$\begingroup\$ Show us a schematic of what you built. \$\endgroup\$ – Matt Young Jan 2 '15 at 2:53
  • \$\begingroup\$ Edit then use Ctrl+M to insert schematic. We need to see what is driving the emitter, base, and collector, as well as which nodes you are measuring. \$\endgroup\$ – MarkU Jan 2 '15 at 2:55
  • \$\begingroup\$ Also maybe tell us what "emitting power" means. What kind of power? How is it emitting it? What did you do, what did you expect, and what actually happened? \$\endgroup\$ – Phil Frost Jan 2 '15 at 3:02
  • \$\begingroup\$ We need a schematic. You can use our integrated CircuitLab tool while editing your post to create a schematic \$\endgroup\$ – Funkyguy Jan 2 '15 at 4:44

The base-emitter junction forms a diode. If the base voltage is higher than the emitter voltage by more than about ~0.6V, current will flow even if there's nothing attached to the collector.


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