Transistor that *Stops* current when base is powered

[NotASmurf]

Hello, in a small scale project I need a way to get 7 outputs from 3 inputs, I have an idea how to do that using transistors but the cost adds up due to the high amount of transistors, it would simplify things space wise, and cost wise if I could eliminate the NOT gates, is there such a thing that blocks power from emitter to collector when base is on instead of the contrary? Any help appreciated.

 

[NascentOxygen]

Electronics can achieve anything. Perhaps if you explain in detail what you are wanting, we can suggest a solution.

 

[soarce]

Why don't you use a specialized BCD decoder ?

 

[Svein]

is there such a thing that blocks power from emitter to collector when base is on instead of the contrary?

You need to define "on". If "on" is "close to the supply voltage", a PNP will turn off.

 

[cabraham]

A JFET is a depletion-mode device. When the gate to source voltage is zero, the device is ON. In order to turn it OFF, the base must be driven negative, for an n-channel part.

Claude

 

[Svein]

Hello, in a small scale project I need a way to get 7 outputs from 3 inputs,

Several possibilities. You could reinvent DTL (Diode-Transistor Logic) or (as mentioned above) get hold of a decoder (they are not much more expensive than transistors). See for example http://www.onsemi.com/PowerSolutions/product.do?id=MC14028B
or http://www.ti.com/lsds/ti/logic/decoder-encoder-multiplexer-products.page#p1512=CD4000

 

[donpacino]

Hello, in a small scale project I need a way to get 7 outputs from 3 inputs, I have an idea how to do that using transistors but the cost adds up due to the high amount of transistors, it would simplify things space wise, and cost wise if I could eliminate the NOT gates, is there such a thing that blocks power from emitter to collector when base is on instead of the contrary? Any help appreciated.

As others have said you should look into decoders.
To answer your question, you want a depletion mode MOSFET. The device acts as a 'closed switch' with an open gate or low gate voltage. you need to pass above the gate threshold to 'turn the switch off.' 1-4 VGS_on typically depending on the device