Why FET has lower thermal noise than BJT?
BJT’s are noisier than FET’s. A BJT is having two pn junctions whereas an FET is having only one pn junction. Hence charge carriers will have to cross more depletion regions in BJT and hence the possibility of addition of thermal noise and minority charge carriers is much higher.
Why there is no thermal runaway in FET?
Detailed Solution. 2) Since the current is decreasing with an increase in temperature, the power dissipation at the output terminal of a FET decreases or we can say that it’s minimum. So, there will be no Question of thermal Runway at the output of the FET.
Why BJT is not suitable for low temperature?
Bipolar transistors are generally preferred over MOS transis- tors because of their lower spread. However, at deep-cryogenic temperatures, the performance of BJTs deteriorates due to a significant reduction in current gain and a substantial increase in the base resistance.
Why FET has better thermal stability?
More thermal stability. FET has a negative temperature coefficient at high current levels. It prevents the FET from thermal breakdown issue. In IC fabrication, BJTs are occupying more space.
What is the effect of temperature on FET parameter?
➢ Increasing the temperature of an FET tends to decrease the mobility of the charge carriers in the channel, effectively reducing the current through the channel. ➢ Simultaneously however, increasing the temperature also narrows the depletion regions of the pn junctions, thereby increasing the drain current.
Why do JFETs offer better thermal stability than BJTs?
Since both the mechanisms occur simultaneously, the effect of one mechanism compensates for the other. JFET offer better thermal stability as compared to BJTs. Increase in JFET temperature results in decrease in the depletion region width and decrease in the carrier mobility.
What is the difference between a BJT and a FET?
• FET is relatively immune to radiation but BJT is very sensitive. • It is a majority carrier device. • FET is less noisy compare to BJT. It is more suitable for input stages of low level amplifiers.
Why BJT transistors produce more gain than FET transistors?
So if you use the same amount of power at the input for both a BJT and FET transistor, the BJT transistor will produce more gain. This is why BJTs are more popular for amplifier circuits. They produce gain than a FET can. This is why in the case of simple amplifier circuits, the use of a BJT is preferred and FETs are rarely used.
What is the leakage current of BJT and FET?
BJT leakage current or reverse saturation current is highly sensitive to temperature. It doubles for every 10 degree celsius. There is no leakage current in FET which makes it thermally stable as compared to BJT.