I know the textbooks say that they can be either or but the way I see it, if they're used as a switch then they are 'amplifying' current. And when they say amplifying they really throw me off because I picture it as the current just increasing in energy out of nowhere...am I right to say that it doesnt amplify anything, it just controls a larger current so technically a transistor is ALWAYS a switch AND an 'amplifier'?
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Transistors...switches and/or amplifiers? (1 Viewer)
- Thread starter LlamaBoi
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I'm a bit fuzzy on transistors, but I'll give it a shot.
They don't really amplify the current, they just act as a valve, which allows more current to pass through the circuit. They replaced thermionic valves right? They do the exact same thing, just in a different manner. Basically what happens is: current is applied to the base, the amount of current dictates how 'open' this 'valve' is. If there is no current applied to the base, no current will be able to pass through the transistor, and it will be 'off'.
Someone confirm?
Edit: Pretty sure this is outside the syllabus anyway.
They don't really amplify the current, they just act as a valve, which allows more current to pass through the circuit. They replaced thermionic valves right? They do the exact same thing, just in a different manner. Basically what happens is: current is applied to the base, the amount of current dictates how 'open' this 'valve' is. If there is no current applied to the base, no current will be able to pass through the transistor, and it will be 'off'.
Someone confirm?
Edit: Pretty sure this is outside the syllabus anyway.
Last edited:
Demise
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I don't think you need to know that in that much depth. Transistors/Switches replaced thermionic devices in order to improve communication. Thermionic devices lacked durability, were unreliable, had a high start-up time, heavy and did not last long whatsoever. The invention of transistors saw the period of improved communication, implementing it into internet communications and other communication devices.
Gather, process and present secondary information to discuss how shortcomings in available communication technology lead to an increased knowledge of the properties of materials with particular reference to the invention of the transistor
You just needed to say the lack of practicality with thermionic devices led to the accelerated development of the transistor.
identify data sources, gather, process, analyse information and use available evidence to assess the impact of the invention of transistors on society with particular reference to their use in microchips and microprocessors
Improved communication in microchips and microprocessors with mobile phones. Good flow of information, newer job sectors, although decreased employment due to automation of workforce tasks.
Gather, process and present secondary information to discuss how shortcomings in available communication technology lead to an increased knowledge of the properties of materials with particular reference to the invention of the transistor
You just needed to say the lack of practicality with thermionic devices led to the accelerated development of the transistor.
identify data sources, gather, process, analyse information and use available evidence to assess the impact of the invention of transistors on society with particular reference to their use in microchips and microprocessors
Improved communication in microchips and microprocessors with mobile phones. Good flow of information, newer job sectors, although decreased employment due to automation of workforce tasks.
someth1ng
Retired Nov '14
The current that can pass through the emitter-collector circuit depends on the current through the emitter-base circuit.
This is due to the electric field produced in the pnp (or npn) junction which opposes the flow of current since a transistor is essentially two diodes, one np junction will not resist the current but the other will. The 'other' electric field can be overcome by the emitter-base current allowing current to flow.
kiinto is correct in saying that a transistor is more like a valve, current through the emitter-base circuit determines the conductivity of the npn or pnp junction and hence, the current in the emitter-collector circuit that can pass.
BrightFella
Member
The more you understand the better your responses will be. The key is then to keep it succinct.
The amplification part is that the current in 'internal' emitter-collector circuit is in proportion to the current in external emitter-base circuit. The proportion constant is huge so you get huge amplification. So say the external circuit contains some electric current that if you connected to a speaker would make really soft musical sounds. When connected to transistor, the current in internal circuit is massively higher than external one but proportionate to it and if you connected internal current to speaker (actually there are usually other parts like capacitors involved in actual amplifiers) it would play much louder music. Actually extra POWER is released since internal voltage is same but there is more current in internal circuit (use P=VI).
Yes when it acts as a switch it is amplifiying in the ON position. But when it is amplifying music the music is never OFF it just has low current/sound.
The amplification part is that the current in 'internal' emitter-collector circuit is in proportion to the current in external emitter-base circuit. The proportion constant is huge so you get huge amplification. So say the external circuit contains some electric current that if you connected to a speaker would make really soft musical sounds. When connected to transistor, the current in internal circuit is massively higher than external one but proportionate to it and if you connected internal current to speaker (actually there are usually other parts like capacitors involved in actual amplifiers) it would play much louder music. Actually extra POWER is released since internal voltage is same but there is more current in internal circuit (use P=VI).
Yes when it acts as a switch it is amplifiying in the ON position. But when it is amplifying music the music is never OFF it just has low current/sound.