Input impedance is a measure of the amount of resistance a circuit presents to a signal being inputted into it. It is typically measured in ohms and is important in determining the overall performance and behavior of a circuit.
Input impedance is important because it affects the flow of current and voltage in a circuit. A high input impedance means that very little current will be drawn from the source, while a low input impedance means that more current will be drawn. This can impact the accuracy and stability of the circuit's output.
A high input impedance is typically anything above 1 megohm (1 million ohms). This is often seen in amplifiers and other circuits that require a strong and accurate input signal without drawing too much current.
A low input impedance is typically anything below 1 kilohm (1,000 ohms). This is often seen in circuits that require a larger amount of current to function properly, such as power supplies or motor control circuits.
The input impedance of a circuit can be determined by measuring the voltage and current at the input and using Ohm's law (V=IR) to calculate the resistance. It can also be determined through circuit analysis techniques such as Thevenin's theorem or by consulting the circuit's datasheet or specifications.