Electronic devices can be divided into two main types: passive and active devices based on functionality.

## Passive devices

In general, resistors, capacitors, inductors are defined as passive devices.

## Opponent

A resistor is a passive electrical component whose function is to bring a resistor to the current of an electric current in an electrical circuit to limit the current. The magnitude of the flow resistance is called the resistance strength. A higher resistance value indicates a higher current resistance. The resistance is measured in ohms (Ω) and the equation is as follows.

R = V / I

Voltage (V), current (I) and resistance (R) are related to Ohm’s law. that is, V = IR. The higher the resistance R, the lower the current I is for a given voltage V over it. It is a linear unit.

The resistors dissipate the electricity supplied by P = I² R Watt or Joule / sec.

## Resistance

The resistors are made of different materials, such as carbon film, metal film, etc. However, we focus on the most common variants and their properties.

Resistance values range from milliohm to megohm, and tolerances for typical resistors range from 1% to 5%. However, the tolerances of precision resistors range from less than 1% to 0.1% to 0.001% and are therefore more expensive and used in analog circuits where a precise / reference voltage is required. Common resistors are available with a maximum power of 1/8 (0.125 W), 1/4 W (0.25 W), 1/2 W (0.5 W), 1 W, 5 W. Based on values and values power, SMD resistors are produced as different size codes 1210, 1206, 0805, 0603, 0402, 0201. It also includes a network of resistors for the R packets used to pull up / down the circuit interfaces.

## Different types of resistors depending on size and shape

Through the hole resistor

SMD / SMT surface mounted resistor.

Different types of resistors depending on the application

Common resistor: used in current limitation, setting errors, voltage dividers, pull-up, filtering, terminating resistors, load resistors, etc.

Precision resistor for voltage feedback circuits, voltage instructions.

Current identification resistor

Power resistor

Parameters for selecting the resistance

When selecting any circuit resistor, the designer must consider the following parameters based on the application and the property of the circuit board.

Resistance value (R),

The force (s) evaporated above

Tolerance (+ / -%)

The size is based on the free space on the circuit board.

Resistance manufacturers: AVX, Rohm, Kemet, Vishay, Samsung, Panasonic TDK, Murata etc.

## Condenser

A capacitor is a passive electrical component whose function is to store electrical energy and supply it to the circuit when needed. The capacity of a capacitor to store an electric charge is known as the capacitor capacity. It is marked with (C). The unit of capacity is Farad (F) and can vary from micro Farad (µF) 1x 10-6 F, Kilo pico Farad (KpF) or nano Farad (nF) 1x 10-9 F pico Farad (pF) 1x 10-12 F. Typical values from 1pF to 1000uF.

**The different uses of capacitors are:**

It blocks direct current and allows AC power to connect circuits.

It bypasses unwanted signal frequencies on the ground.

It is used to change the phase and to create delays.

It is also used for filtering, especially to remove waves from a corrected waveform.

It is used to reach a set frequency.

It is used as an engine starter.

The capacitor equation is given as follows;

C = Q / V

Where Q is the load and V is the capacitor voltage and C is the capacitance.

Since the current i = dq / dt, ie the rate of change of the charge,

Thus I = C dV / dt

## Capacitor symbols

Therefore, if the voltage on the capacitor is constant, no current flows through the capacitor; and the current flows only on the capacitor if the voltage on it changes over time, e.g. alternative current. Therefore, the capacitor blocks direct current signals and allows only alternating current signals to pass when used in a number of signal paths.

The energy stored in capacitor C was charged until the voltage V is reached

E = 1/2 CV²; where V is in volts and C is in capacity

Although the ideal capacitor does not offer resistance and inductance, in a real capacitor it has a small amount of effective resistance in series due to the capacitor plates, dielectric material and connecting wires. A higher ESR increases the noise on the capacitor, which reduces the filtration efficiency, so the ESR must be lower.

A capacitor consists of two para plates(conductors) separated by a non-conductive region formed by a conductor, for example a dielectric.

C = ε A / d

Where A is the area of the plate, d is the distance between the two plates and ε is the dielectric constant. Dielectric materials can be air, paper, ceramic, plastic, mica, glass, etc.