When looking at digital electronics it's very common to see capacitors placed very close to the power connections of integrated circuits. This can be particularly useful when you have a signal that you need to bias to a center voltage for single-ended analogue to digital conversion using a micro-controller.Ĭommon Digital Electronics Configurations Decoupling Capacitors oscillating around 0V, or you can apply a new DC bias to reference the signal to a new bias voltage. Once you have blocked the DC with the capacitor, you can either leave the signal as unbiased, i.e. This capacitor must be of non-polarised type, so no electrolytic capacitors! The larger the capacitor, the less attenuation this will have for lower frequencies, but DC will be blocked. If you put a capacitor in the signal path, this effectively creates a high pass filter and only the signal may pass. The DC blocking capabilities of capacitors can be used to remove DC bias from a signal, or to apply a DC bias to a signal. Voltage rating will always given for a capacitor, this is the DC voltage that can be applied before the dielectric material between the capacitor plates will break down and begin to conduct. This means that capacitors actually block DC voltage. There is no direct electrical connection. We can further improve on our understanding by looking at the circuit symbol for a capacitor, or by imagining the mechanical construction. We can see that if frequency reduces to "0", meaning DC, the impedance increases to infinity, as we end up dividing by "0". If we use the equation for impedance of a capacitor: As with the passive low pass filter we can see that this capacitor and resistor configuration forms another frequency dependent potential divider allowing higher frequencies to pass more easily and attenuating the lower frequencies, to the point of a complete block of DC signals.