Disadvantages of BJT and JFET

Here, we are going to discuss the Disadvantages of BJT and JFET

Disadvantages of Bipolar Junction Transistor (BJT)

• Lower Input Impedance: BJTs have usually poor input impedance than what is offered by JFETs that may not be applicable in a case where a high input impedance is needed.
• Temperature Sensitivity: BJTs have the temperature variation sensitivity that may lead to the degradation of actuation performance and overheat problems and cause a need to make appropriate temperature compensation measures.
• Higher Noise Levels: BJTs display worse noise output than JFETs, therefore much less suitable for applications which prioritizes noise reduction.
• Complex Biasing: The BJTs tend to have greater complexities in their biasing arrangements compared to the JFETs which in turn introduces the system to more shading.
• Power Consumption: The typical BJTs consume more power, than the JFETs and in case of the power efficient designs or the devices based on batteries, this factor is not highly desired.

Disadvantages of Junction Field-Effect Transistor (JFET)

• Limited Voltage Gain: Normally, JFETs have lower voltage gain compared to BJTs, so stages of extra amplification may be necessary in certain situations.
• Slow Switching Speeds: JFETs comparable but the switching time—they are not suited for the high-frequency applications.
• Sensitivity to Overvoltage: When powered above the voltages that they are designed, a JFETs can be damaged, thus, the usage of a protection measures are strict to prevent damages.
• Limited Voltage Ratings: The JFETs could have lower voltage ratings instead of some BJTs having higher power outputs thus limiting the applications of the second arbitrary order parameter.
• Variability: These very critical JFET parameters may significantly differ in each individual device, so those parts must be chosen and matched scrupulously for precise tasks.

Bipolar Junction transistors (BJT) & Junction Field-Effect transistors (JFET) are important components that are used in many electronic circuits, which are based on semiconductors. In a BJT, there are three different layers of semiconductor material: N-type and P-type semiconductor material forming either an NPN or PNP configuration. As its functioning principle is based either on the movement of electrons via the junction or the flow of holes from the emitter to the collector terminal, it is one of the most effective and robust devices.

As JFET’s counterpart, the gate features a channel in which semiconductor material either will be N-type or P-type. The flow of current in a JFET is governed by a voltage being connected across the junction, which is responsible for the variation in the channel’s width and, in turn, the current between the source and drain terminals. 

The JFET, unlike the BJT, works mainly on the ground of the voltage rather than the current. As for BJT and JFET, these two components exhibit key roles in amplification, switching, and signal processing applications supporting the design diversity of circuits through their peculiar traits and features.