Why input impedance of MOSFET is higher than BJT?

Why input impedance of MOSFET is higher than BJT?

MOSFETs have a higher input resistance than JFETs, which in turn have a much higher input resistance than BJTs (assuming “normal” operation – not out-of-range input voltages that trigger any MOSFET gate protection zeners or put the JFET gate into a situation where it conducts).

In which the input impedance is highest?

Which among the following circuit has the highest input resistance? Explanation: Voltage follower has the highest positive input resistance of any op-amp circuit. For this reason it is used to reduce voltage error caused by source loading.

Does MOSFET have high input impedance?

The oxide layer, effectively a dielectric, acts as a capacitor and isolates gate and rest of the substrate body, source, drain and channel. Hence no connection exists between gate and rest of the parts, which means input impedance of a MOSFET is very high.

What is input impedance of MOSFET?

mosfet input impedance The gate lies on an insulated thin oxide layer (dielectric) above the substrate between the source and drain. The gate is effectively one side of a capacitor. This is the input impedance being referred to – the fact that the gate has no DC path to either source, drain or substrate.

Is BJT input impedance high?

BJTs offer smaller input impedances, meaning they draw more current from the power circuit feeding it, which can cause loading of the circuit. FETs offer greater input impedance than BJTs. This means that they practically draw no current and therefore do not load down the power circuit that’s feeding it.

What is the input impedance of BJT?

BJT Amplifier Input/Output Impedance Input impedance is defined as the ratio of imput voltage to input current. It is calculated from the AC equivalent circuit as the equivalent resistance looking into the input with all current cources replaced by an open and all voltage sources replaced by a short.

What is the input impedance of Mosfet?

As oxide layer is dielectric there is no question of drawing current so obviously, input impedance is infinite.

What is the difference between a BJT and a MOSFET?

The input impedance of BJT is low on the other hand input impedance of MOSFET is high. BJT and MOSFET are two different transistors, BJT is a transistor itself and MOSFET is a type of FET transistors. Both of them are used in different fields for different devices.

What is the working of a MOSFET?

MOSFET working depends upon the MOS capacitor which is the semiconductor surface between the source and the drain. their infinite input impedance allows the amplifier to catch almost all signals. It has three terminals; source, gain and drain. One of the advantages of MOSFET is that it does not require input current to control the load current.

How many layers are there in a basic BJT transistor?

BJT transistor consists of mainly four layers; the first layer is the emitter layer (n+) which is heavily doped, the second layer is the base layer (p) which is moderately doped, third layer collector drift region (n-) which is lightly doped, and the fourth layer collector region (n+) which is highly doped.

What type of biasing is used in emosfet?

Self bias& Voltage divider biasing. In DMOSFET we use self bias and voltage divider biasing, in EMOSFET we use feedback bias and voltage divider biasing. Active, Saturation & Cut off region.