Transistors?

Question

How does a transistor "amplify" current in a circuit?

In response to this comment:
By sending varying levels of current from the base, the amount of current flowing through the gate from the collector may be regulated. In this way, a very small amount of current may be used to control a large amount of current, as in an amplifier.

Right. My question is, why use a transistor to do this, when you can just make a parrallel circuit, one segment of high resistance, and one of low resistance.

Answer 1

Even when I remembered the physics of a transistor, I couldn't describe it simply. In a bipolar transistor, a small current applied to the base-emitter junction allows a much larger current to flow through the collector-emitter junction. It's a little like using a small effort to open a valve and control a large flow.

Answer 2

The transistor can function as an amplifier or a switch. This is accomplished by using a small amount of electricity to control a gate on a much larger supply of electricity, much like turning a valve to control a supply of water.

Transistors are composed of three parts – a base, a collector, and an emitter. The base is the gate controller device for the larger electrical supply.

The collector is the larger electrical supply, and the emitter is the outlet for that supply.

By sending varying levels of current from the base, the amount of current flowing through the gate from the collector may be regulated. In this way, a very small amount of current may be used to control a large amount of current, as in an amplifier.

Answer 3

Not only are the other answers correct, one very important detail has been left out, going to a more powerful transistor is going to get you no where, except maybe to a burned out power supply, or worse. EP since it is apparent that you do not have the skills needed. stay with what you have. To effectively use a more powerful output transistor, of the BJT kind, forget the MOSFET, you need to increase the drive from the existing drivers, improve the power supply, be sure that the output circuitry will handle the new load without changing output impedance, and that the heat sink is rated for the new load. One possible answer for the driver stage is to use Darlington pair type output transistor. While this takes care of the driver issues, it does nothing for the power supply, output impedance issues, nor the heatsink. If these things are not scaled properly, or modified as needed, you might end up with a small scale variation of the Hiroshima mushroom cloud, but without the radiation. Keep what you have, and go buy a new amp.

Answer 4

difficult to explain without graphics bu here goes.

Imagine a transistor to be like a sandwich. the bread is, say, P doped silicon and the filling would be N doped silicon.
Where the Ps meet the N there is potential junction like a diode.
The junctions on each side of the N limits the current that can flow but if you supply a small voltage to the Ps the 'depletion zone is either reduced or increased depending on the polarity of the applied signal. The change in depletion zone size varies the current that can flow through the N. The ratio of signal current to the output current is called the 'gain' of the transistor and it is determined by the construction of the transistor.

Answer 5

The how has been answered. Here is the why:
In order to create varying resistance in parallel, as you suggested, one would have to use a varying resistor. This is possible using mechanical devices, and is what is used to control volume in many devices. The problem is, this requires mechanical operation, which prohibits other parts of the circuit from controlling it efficiently.

Transistors do, in fact, create varying resistance in the channel by pushing 'minority carriers' to the surface of the gate, or away from it, forming a 'depletion region'. So transistors are, in a nutshell, exactly what you proposed: varying resistors in parallel. You can even model them in circuit analysis this way.

Answer 6

Transistors take a varying input and it controls a higher voltage output that is identical to the single coming in.
The link go into more detail and further down is a picture.
http://www.tpub.com/neets/book7/25c.htm

Answer 7

Try the one segment of high resistance, and one of low resistance at 1000Mhz at the same precise time