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

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⚙️ 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

 

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🔍 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

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⚡ 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

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📲 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.

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🛠️ 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

 

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🔧 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

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