I was going through data sheets of op amps and saw that bias currents usually add unwanted voltages due to voltages generated from the bias current flowing through the source impedances.
What exactly does the source impedance mean ?
I understand what impedance is, but since there could be a lot of circuitry before the input to the op amp, do we just use normal laws to calculate the total resistance/impedance before it(input) ?
There also might just be a power supply providing constant DC voltage , how are we supposed to calculate the impedance of that ?
Best Answer
The device that supplies a voltage signal or a dc power voltage is the source. The source impedance is the internal resistor in series with that otherwise perfect source voltage.
A battery for instance may have a source impedance of about 0.1 ohms. See this link to Duracell's website and click on the pdf for an AA battery: -
It's the same for linear voltage regulators, microphones and anything that can generate an AC or DC voltage - there will be some internal resistance that may have to be taken into account when the device is connected to a load.