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Is BJT 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.
Why FET is called voltage controlled voltage devices?
A FET is voltage controlled device by virtue of the fact that current flow between the Drain and the Source is controlled by the voltage at the Gate in reference to the Source (Vgs). a fet is controlled by a voltage at the terminal of the gate and, because of the very high grid impedance, flows in or out of the gate.
Why FET is preferred over BJT?
Since this input impedance is considerably higher than that of BJTs, FETs are preferred over BJTs for use as the input stage to a multistage amplifier. One class of FETs (JFETs) generates lower noise than BJTs. FETs are more temperature stable than BJTs. FETs are generally easier to fabricate than BJTs.
Is SCR a voltage controlled device?
SCRs are mainly used in devices where the control of high power, possibly at high voltage, is needed. The ability to switch large currents on and off makes the SCR suitable for use in medium to high-voltage AC power control applications, such as lamp dimming, regulators and motor control.
Why are BJT and FET called current / voltage controlled voltage / current?
Hence, there is no current flow into the gate. Therefore, it must be a voltage-controlled device. Specifically, the channel resistance is a function of the gate to source voltage. Incidentally, that high resistance looking into the gate makes for a nasty capacitor to charge, hence the need for FET drivers on occasion.
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.
How is a BJT different from a FET?
A bit awkward question but still it confuses me…… 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 is a FET a voltage controlled source?
A FET has a high impedance control input (the gate) and as such it cannot accept current making it a voltage controlled device if you use it in a common source configuration.