# Common Circuit Elements

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This page gives a few common circuits or component configurations and their general applications.

## Common Analogue Configurations

### Bridge Rectifier

Bridge rectifiers are commonly found in power supply circuits and other situations where AC needs to be converted to DC. It relies on a configuration of 4 diodes which prevent conduct at different times during the AC cycle of the system. In the image shown, diodes D1 and D3 will conduct during the positive part of the cycle, and diodes D2 and D4 will conduct during the negative part of the cycle. This leads to the output waveform shown which is all positive when referenced to the connection of D3 and D4's anodes when capacitor C1 is NOT present.

The capacitor C1 can be added to the output to smooth the rectified positive signal. The size of capacitor C1 will be determined by the load that is placed on the output and the "ripple" requirements of the circuit. As the load on the output increases it will increase the ripple in the DC voltage level as C1 is discharged more aggressively.

### Potential Divider

Potential dividers can be used to take an input voltage and divide it using the ratio of R1:R2 to give some smaller output voltage. The equation to calculate the output voltage is as follows$V_{out} = V_{in} * \frac{ R_{2} }{ R_{1} + R_{2}}$

### Low-Pass Filter

The passive low pass filter is one of many kinds of filter circuit which is intended to pass frequencies below some defined value and attenuate to some degree, frequencies above that value. If we remember from the Basic Electronics Design section, that capacitors have a frequency dependent impedance, it becomes clear that this resistor capacitor combination basically forms a frequency dependent potential divider.

### High-Pass Filter

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.