Resistors in Mobile Phones: Types, Functions & Working Explained (2026 Guide)

Resistors in📱 Introduction

Resistors are one of the most basic yet critical components used in mobile phone circuit boards.

Whether it’s charging, signal processing, or power management, resistors play a vital role in ensuring proper functioning of the device

⚙️ What is a Resistor?

A resistor is a passive electronic component that limits or controls the flow of electric current in a circuit.

It helps maintain proper voltage levels and protects sensitive components from damage.

👉 In simple terms:
Resistor = Current Controller

It looks black in color

🔍 Types of Resistors Used in Mobile Phones

1. SMD Resistors (Surface Mount Device)

- Most commonly used in smartphones
  Very small in size

- Mounted directly on PCB (Printed Circuit Board)

2. Zero Ohm Resistor (Jumper)

- Acts like a wire (no resistance)

3. Thermistors

- A thermistor is a temperature-sensitive resistor whose resistance changes significantly with temperature.

- It is widely used in mobile phones for temperature sensing, protection, and control.

- 👉 Simple definition:
  Thermistor = Temperature-dependent resistor

Types of Thermistors

🔵 1. NTC (Negative Temperature Coefficient)

- Temperature ↑ → Resistance ↓

- Most common in smartphones

- Used in battery and charging circuits

🔴 2. PTC (Positive Temperature Coefficient)

- Temperature ↑ → Resistance ↑

- Less common in mobile phones

⚡ Working Principle of Resistor

Resistors work based on Ohm’s Law, which states:

👉 V = I × R

Where:
V = Voltage
I = Current
R = Resistance

✔️ How it Works:

- When current flows through a resistor, it opposes the flow

- This opposition converts some electrical energy into heat

- As a result, current is controlled and stabilized

📲 Functions of Resistors in Mobile Phones

🔋 1. Current Limiting

Prevents excessive current from damaging components like ICs and LEDs.

🔌 2. Voltage Division

Resistors divide voltage into required levels for different circuits.

📡 3. Signal Conditioning

Used in communication circuits to stabilize signals.

🔄 4. Pull-Up & Pull-Down Function

Ensures proper logic levels in digital circuits (HIGH or LOW states).

🔥 5. Protection

Acts as a safeguard against short circuits and overload conditions.

🛠️ Practical Use in Mobile Repair

Common Faults Related to Resistors:

- Missing resistor → Circuit not working

- Burnt resistor → Overheating issue

- Faulty NTC Thermistor → ⚠️ “Battery temperature too high/low” error ,🔄 Boot loop in some cases

- SMPS Resistor open or high value →Mobile Dead

- Faulty Resistor → Fake Charging

🔧 Checking Resistor with Multimeter (Quick Steps

- Set multimeter to Ω (resistance mode)

- Ensure phone/PCB is powered OFF

- Identify the SMD resistor (small black component)

- Place probes on both ends of resistor (no polarity)

- Read the value on display

📊 Result Interpretation

- ✅ Correct value → Resistor OK

- ❌ OL / no reading → Open (faulty)

- ❌ 0 or very low → Shorted

- ⚠️ Wrong value → Damaged / drifted