When using the network analyzer to measure impedance, such as the capacitance and ESR or a capacitor, or the DCR of an inductor, etc., it is often necessary to provide a voltage bias to the device being tested. This is true of semiconductor junction capacitances, varactors, and some ceramic capacitors (especially X5R). In these cases the impedance is a function of the DC bias on the device. The Picotest DC bias injector (J2130A) is used for this purpose during impedance measurements.