The answer is the high input impedance is good for the amplifier circuit to have a good amplification of the input signal other wise we get low voltage in, so low amplification.
In this way, what is a high impedance voltmeter?
An ideal voltmeter has infinite input impedance, meaning that it draws zero current from the circuit under test. This loading is more pronounced on circuits of high resistance, like the voltage divider made of 1 MΩ resistors, shown in the schematic diagram.
Why the input impedance of FET is so high?
Contrast this with the BJT. Hence, a BJT is current controlled , where as a n FET is voltage controlled. Naturally, you know that a reverse biased diode junction is like a open circuit, showing ideally infinite impedance. So, the reverse biased gate input of the FET is the cause of its high input impedance.
What is a high impedance fuel injector?
High-impedance injectors, also called saturated fuel injectors, are sent a 1–1-1/2-amp current signal to open, and that current stays on until the injector closes. Low-impedance injectors, also called peak-and-hold injectors, are sent a more powerful electrical signal, usually around 5–6 amps, to open.
What is output impedance on a microphone?
This is a measurement of the AC resistance looking back into the microphone. Generally, microphones can be divided into low (50–1,000 ohms), medium (5,000–15,000 ohms) and high (20,000+ ohms) impedance. There is a limit to how much cable should be used between a high-impedance microphone and its input.