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Why is BJT called a current controlled device and FET a voltage controlled?
A BJT is a current controlled device because its output characteristics are determined by the input current. A FET is voltage controlled device because its output characteristics are determined by the Field which depends on Voltage applied.
Why JFET is called voltage control device?
JFET is a three-terminal device and since gate voltage controls the drain current, JFET is called a voltage-controlled device. JFET’s have only a depletion mode of operation. Thus drain current in JFET is controlled by changing the channel width.
Is a JFET is voltage or current controlled device?
Unlike bipolar junction transistors, JFETs are exclusively voltage-controlled in that they do not need a biasing current. Electric charge flows through a semiconducting channel between source and drain terminals.
Is BJT a voltage controlled current source?
BJTs can be thought of as voltage-controlled current sources, but are more simply characterized as current-controlled current sources, or current amplifiers, due to the low impedance at the base. Early transistors were made from germanium but most modern BJTs are made from silicon.
How many gates does a JFET have?
three
Like the BJT, the JFET is a three-terminal device. The terminals are called the source, drain, and gate. They are similar in function to the emitter, collector, and base, respectively.
Is BJT is a voltage controlled device?
Which one of the following is voltage controlled device?
Explanation : All field effect transistors are voltage controlled devices.
Which is a current controlled device BJT or FET?
FE’T is a voltage controlled device, i.e. voltage at the input terminal controls the output current, and whereas BJT is a current controlled device i.e. the input current controls the output current. As shown in the Fig. 2.6, in BJT the output current, I_C is controlled by the base current I B. Hence BJT is a current controlled device.
Why is BJT called current / voltage controlled voltage / current?
In a BJT, the base is connected to the emitter via an internal resistance. The resistance is in the low ohms. Therefore, there is a means for current flow. Hence, the BJT is a current-controlled device. Specifically, the current through the device (collector to emitter — assuming an NPN) is a function of the current into the base.
What makes a FET a voltage controlled device?
Therefore, FET is a voltage controlled device. The name “field effect” is derived from the fact that the output current flow is controlled by an electric field set up in the device by an externally applied voltage between gate and source terminals.
How is the source drain of a BJT controlled?
FETs in general, source-drain current is controlled with a very little current from the gate. BJTs require more current, because of how it works, collector-emitter current is proportional to the current from the base.