Transistors acting as resistors

In summary, transistors can act as resistors with varying resistances depending on the type and mode of operation. Bipolar transistors typically have a larger resistance in the order of kiloohms while MOSFETs have a smaller resistance in the order of milliohms. The specific resistance can be found in the transistor's datasheet. Additionally, certain MOSFETs can be used as voltage-controlled variable resistors.
  • #1
mvpshaq32
28
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From what I understand, transistors can be viewed as several things, one of which is a resistor.

So how much resistance is a transistor turned on generally equivalent to?

And what is normally considered a large or small resistance? I know voltmeters have a large internal resistance in the order of megaohms. And I believe transistors are in the order of kilos, so would transistors acting as resistors be considered as having a low resistance?
 
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  • #2
Some bipolar transistors, when turned fully on, will have a voltage drop across the collector and emitter of approximately 0.3 volts (silicon based).

For MOSFET's, when turned fully on, there is a on-resistance in the order of milliohms. I would suggest looking at the datasheet for the transistor using.

If you are using the small-signal model of a transistor then you will be able to describe it as resistors and controlled current/voltage sources.
 
  • #3
Certain MOSFETS are used a voltage-controlled variable resistors. Google "Siliconix VCR"
 

1. What is the purpose of using transistors as resistors?

Transistors can act as resistors in electronic circuits to regulate the flow of current and voltage. They can be used to control the amplification of signals, switch between different circuits, and reduce the amount of current flowing through a circuit.

2. How do transistors act as resistors?

Transistors have three regions - the base, emitter, and collector, each with different levels of conductivity. By controlling the flow of current between these regions, transistors can act as resistors and regulate the amount of current and voltage in a circuit.

3. Can transistors completely replace traditional resistors?

While transistors can act as resistors, they cannot completely replace traditional resistors. Transistors have limitations in terms of their maximum power handling capabilities and can be more expensive than resistors. In some cases, using a combination of transistors and resistors may be more efficient.

4. How do the properties of a transistor affect its resistance?

The resistance of a transistor can be affected by its material, size, and configuration. For example, a larger transistor will typically have a lower resistance compared to a smaller one. The type of material used can also impact the resistance of a transistor.

5. Can transistors act as both resistors and amplifiers?

Yes, transistors can act as both resistors and amplifiers. By controlling the amount of current flowing through the transistor, it can regulate the amplification of a signal. This makes transistors a versatile component in electronic circuits.

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