Hi,

Newbie question.....


I am testing a simple inverter I made as per

http://www.kpsec.freeuk.com/trancirc.htm

At the output I have connected a LED via a resistor.

Problem: The output ( LED ) is always ON whether the base current is switched on or switched off.

I attached a LED after the emitter. And this is OK , ie it comes on only when the base current is on.

Could somebody kindly clarify ?
Thanks in advance.

Venkee

 

The circuit you're trying to use:

The circuit you should be using instead:

See how similar they are?
Basically the same thing. Just put your LED in series with Rc.

 

Thank you SgtWookie.

As I had mentioned, I am testing this circuit and had put the LED only for testing. Actually I need the inverted signal to control another part of the circuit.

How do I do it then ? ie get the inverted waveform....


Searching the net for such NOT-gate-type inverter turns up so many circuits but they are so similar to this....

I dont know what is it that I am doing wrong.


I have been testing the circuit with 4.5 volts.

 

Actually I need the inverted signal to control another part of the circuit.

In this case your first circuit should actually work.

- what transistor are you using?
- how does the circuit you want to control look like?

 

What is the control signal?

Double check your wiring.

 

your circuit may be picking up noise if the base is floating and the transistor is sensitve enough.....both these circuits work(with an additional pull down/pull up resistor)