Compared to BJT, a JFET has :
Higher input impedance and low voltage gain
A BJT is a current-controlled device: its base–emitter junction is forward biased, so its input impedance is only a few kilo-ohms. A JFET is voltage controlled: its gate–channel junction is reverse biased, so the gate draws only a tiny leakage, giving an input impedance of the order of \(10^{8}\) to \(10^{10}\,\Omega\).
The voltage gain of a common-source or common-emitter stage is roughly \(A_v \approx -g_m R_D\) or \(-g_m R_C\). A BJT has \(g_m = I_C/V_T\), which is several tens of millisiemens at a milliampere, whereas a JFET's transconductance is only a few millisiemens. So, compared with a BJT, a JFET offers a much higher input impedance but a lower voltage gain for the same load.
Lower input impedance is the reverse of the true comparison. Higher voltage gain, alone or together with higher input impedance, is wrong because the JFET's smaller transconductance gives less gain than a BJT stage.
Higher input impedance and low voltage gain option is correct.
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.................... is a client server application that identifies each host on the internet with a unique user-friendly name.
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