transistor uses

[Kevin Weddle]

The transistor can be used for many things, yet it operates one way. It can be operated as a linear amplifier. It can be operated at cutoff and saturation. It can be used as a resistance, two diodes, or a voltage converter. It may act as a constant current sink or source. Which funtion do you think might work best?

 

[Guest]

Don't all operations work fine?

 

[nanakis1]

I'll agree with Siddhart. But i think that you might need to secify the question more cleary.

 

[Kevin Weddle]

I don't like using transistors as diodes. It seems tricky enough to get a current multiplier to work. Does anybody really accept the simple model of the transistor?

 

[electrodoc2]

http://www.electronics-lab.com/forum/index.php?board=15;action=display;threadid=794

 

[Kevin Weddle]

I like the representation of a transistor that would use a zener and a diode. This seems more suitable. Does anybody like this idea?

 

[ante1]

Kevin,

What do you figure it could bee used for?

Ante :

 

[Kevin Weddle]

I think it could be used to replace the transistor in some cases. The transistor will not change it's current with a changing collector voltage, but maybe a zener with a diode will. This is certainly a legitmate use that may act similarly to a transistor if the zener and diode were chosen properly. I have no doubt that there exists a circuit which has this combination. The question is, how well will it mimick the transistor. Does anybody follow this assertaion?

 

[ante1]

Kevin,

What characteristics could it have and how would it perform in a circuit? Do you think it would bee an equally

 

[Kevin Weddle]

The reason I thought of this is because I wanted to operate a transistor backwords in a circuit. I wanted the collector to act like an emitter. The nice thing about the collector is high impedance. The nice thing about the emitter is the ability to change the current and pass the signal. You will find that the emitter impedance is typically low because the base current. In other words the two resistors at the base are of small value because the base get's it's current through these two resistors.

As far as the characteristics, I would guess the zener would have to conduct quite a bit when the voltage at the base changes. The zener, under normal conditions, conducts more when the voltage across it exceeds the rated voltage.

 

[ante1]

Kevin,

What kind of operation do you want to do by

 

[Kevin Weddle]

The high impedance, but able to pass the signal. You will find that the two base resistors have to be low value in order to get the base current. This makes the emitter impedance low. I needed a higher impedance for the purpose of gain.

 

[ante1]

Kevin,

In which range do you expect the hfe to be?

Ante :

 

[Kevin Weddle]

I don' know. Do you have the idea that this will work to a certain extent. It becomes a little tricky when you get away from the transistor model, add a 5 layer device it's even more complicated. Maybe as far as the hfe goes, it would depend on the zener conducting heavily with a small change in base voltage. The diode would have to conduct heavily too or else the base current would be too high. You need current to flow from collector to emitter.

 

[ante1]

Kevin,

A 5-layer device? A diode and a Zener, how do you mean

 

[Kevin Weddle]

I would be talking about diacs or triacs when I say a 5 layer device. The anode of the zener would be the base. The anode of the diode would be the base. The cathode of the zener would be the collector and the cathode of the diode would be the emitter.

 

[ante1]

Kevin,

Do you know if this could be possible to simulate, maybe with some software. I think it could be interesting if it was possible. But software like that exist probably only at NASA or some ware in Silicon Valley.

Ante :

 

[Kevin Weddle]

I would just stick it into a beta tester but I don't think it work. You know that it will be a function that has linear properties.

 

[sec]

The high impedance, but able to pass the signal. You will find that the two base resistors have to be low value in order to get the base current. This makes the emitter impedance low. I needed a higher impedance for the purpose of gain.

In that case, you might want to look into using a FET.