Table of Contents
What is the purpose of collector resistance?
The purpose of the collector resistor Rc is to set the collector current Ic as well as the emitter- collector voltage Vce. In other words, Rc helps to set the transistor at the “operating point” of the ampli- fier.
What is the resistance between collector and emitter when an ideal transistor is at cut off?
Basic NPN Transistor Switching Circuit An ideal transistor switch would have infinite circuit resistance between the Collector and Emitter when turned “fully-OFF” resulting in zero current flowing through it and zero resistance between the Collector and Emitter when turned “fully-ON”, resulting in maximum current flow.
What is collector resistance in transistor?
In your example circuit, the collector-emitter junction can be thought of as a variable resistance whose value depends on the electronical situation present at the amplifier’s output. It also heats up like a resistor: Ic * Vc = the amount of heat generated in Watts, heating up the transistor.
Does a transistor need a resistor?
Base Resistors! A transistor without a resistor on the base is like an LED with no current-limiting resistor. Recall that, in a way, a transistor is just a pair of interconnected diodes. We’re forward-biasing the base-emitter diode to turn the load on.
What is re in BJT?
• There are two models commonly used in the small-signal ac analysis of transistor. networks: the re model and the hybrid equivalent model. THE re TRANSISTOR MODEL. • The re model employs a diode and controlled current source to duplicate the behavior of. a transistor in the region of interest.
What happens if collector current increases in a collector emitter feedback circuit?
4. What happens if collector current increases in a collector emitter feedback circuit? Explanation: If the collector current VC is increased, the corresponding emitter current also increases. Which in turn causes the voltage across RE to increase.
Do transistors add resistance?
This is why although a transistor has a defined V and I, and their ratio has units of resistance, we do not say that it has a resistance, because it will be measured differently by different resistance-measuring devices. Two current measuring devices will give substantially the same reading as each other.
Why is a resistor connected to the collector of a transistor?
For an amplifier to work properly, the DC current in the collector must remain constant. but the heat produced causes a modification of the current in this collector. Thus, these resistors attached to the transistor in a basic amplifier circuit are intended to provide bias and stability.
How to add an emitter to a multi collector BJT?
Multi collector bjt’s are useful in IC’s since it is easy to match the ratio between the collector areas and split a polarizing current in precise ratios, as in the uA741 output stage polarization (\\$Q_{13}\\$ here): At solid state level to add an emitter you simply add an emitter diffusion:
How does current flow in a bipolar junction transistor?
In a bipolar junction transistor, current flows from the emitter to the collector and then out from the collector. The reason the emitter is the most heavily doped region is because it serves to inject a large amount of charge carriers into the base, which then travels into the collector, so that switching or amplification can occur.
What determines the gain of a BJT?
The gain of a BJT is influenced strongly by the emitter-base injection efficiency, but since the base region is necessarily thin it is the emitter carrier density (doping level) that determines efficiency. High efficiency requires heavy doping.
What is the most heavily doped area of a transistor?
The emitter region is the most heavily doped area of the transistor. The emitter contains the largest amount of charge carriers out of all regions in the transistor.