Electronic products are often complex masses of PCB, As you peel back the layers of any complex electronic product, common Printed Circuit Board, subsystems, and modules are present. Common circuits are simple circuits that are easy to design, work with, and test. The circuits listed here are common circuits frequently used in electronics.

     1. On/Off Switch

Controlling the power to systems and subsystems is a common need in electronics. Optically isolated relays are the most effective and simplest ways to implement an on/off switch to a sub-circuit.

      2. Resistive Divider

One of the most common Printed Circuit Boards used in electronics is the humble resistive divider.

       3. Level Shifter

Modern electronics are full of chips that require different voltages to operate. Low power processors often operate on 3.3 or 1.8v, while many sensors run on 5 volts. Level shifting chips are the easiest to implement and require few external components, but they all have their quirks and compatibility issues with different communication methods.

        4. Filter Capacitors

All electronics are susceptible to electronic noise that can cause unexpected, chaotic behavior or completely halt the operation of electronics. Also, caps can be used to filter the input of signals to lower the noise on the signal line.

         5. OpAmps

OpAmps are useful in buffering a signal while boosting or dividing the input signal, which comes in handy when a signal needs to monitored without being affected by the circuit doing the monitoring. Also, the boost and divider options allow for a better range of sensing or control.

         6. Voltage References

When precision measurements are required, a known voltage reference is often needed. Voltage references come in a few form factors.

         7. Voltage Supplies

Every Printed Circuit Board(PCB) needs the right voltage to operate, but many circuits need multiple voltages for every chip to work.

          8. Micro controller

Nearly every modern electronic product has a micro controller at its heart.

          9. Current Source

Voltages are relatively simple to work with within a circuit, but for some applications, a steady fixed current is required. High-power versions of current sources require additional components and demand a greater design complexity to accurately and reliably control the current.

           10. ESD Protection

An often forgotten aspect of an electronic product is the inclusion of electrostatic discharge (ESD) and voltage protection. When devices are used in the real world, they can be subjected to incredibly high voltages, which can cause operational errors and even damage the chips.