Question

what does a JFET provide that a normal transistor can't provide ?...they say it has higher impedance but what does that do?

Answer 1

High input impedance is an advantage because it provides greater isolation between the input and the output. Also, a high impedance device will not pull down the signal voltage. Plus, a jfet will be less noisy than a bipolar transistor.

Answer 2

the input will be exactly fed into the terminals of JFET if the input impedence is high if not there will be formation oof a low resistance path and the input may not be able to drive the JFET and maximum current flows through the input terminals .

Answer 3

ramblinrob n giligails have well explained, the benefits of JFET in terms of input transistor. The high input impedance means input current, So if u have provided vdd level signal at input, ur input power consumption is very low. for battery operated ckts, these thing are needed e.g. mobile phones. MOSFET( specially CMOS logic) is even better than JFET, in JFET there is a reverse leakage current at input, But in MOSFET, there is no such case. The CMOS logic provides very low dc power consumption.

Answer 4

But you can't ignore benefits of BJT's. Their high capability of thermal breakdown, And mainly for ESD ( electrostatic discharge) these r much much better than MOSFET's in terms of area in a chip vs performance criteria.