IR Receiver Symbol

The IR Receiver schematic symbol. Standard-specific details are listed below where available.

Definition: The IR Receiver symbol represents a three-terminal integrated infrared demodulator module — such as the TSOP1738 or VS1838B — that detects 38 kHz modulated infrared light from a remote control handset and outputs a demodulated logic-level signal, shown in schematics with OUT (demodulated output), GND (ground), and VCC (supply voltage) terminals, consistent with component block diagram conventions in hobbyist and professional circuit documentation.

Also known as: TSOP receiver, infrared receiver module, IR demodulator, remote control receiver, 38 kHz IR receiver, TSOP1738, VS1838B, infrared remote receiver.

What the IR Receiver symbol means

The IR Receiver symbol denotes a self-contained integrated receiver module that combines an IR photodiode, pre-amplifier, bandpass filter (centred on the carrier frequency, typically 36–38 kHz), envelope detector, and output buffer in a single 3-pin package. The module detects infrared light that has been modulated at the carrier frequency by an IR remote control transmitter, demodulates the signal to recover the original pulse train, and outputs an active-low logic signal on the OUT pin that follows the NEC, RC5, or other remote control protocol data encoding.

In a circuit schematic, the IR receiver symbol identifies the point where infrared remote control commands enter the system. The OUT pin connects to a microcontroller GPIO or interrupt input that decodes the received pulse timing. The VCC pin is powered from the 3.3 V or 5 V supply rail, and the GND pin connects to the circuit ground. A decoupling capacitor (100 nF + 4.7 µF) on the supply pin is recommended to prevent supply noise from disrupting the sensitive receiver front-end.

How to identify the IR Receiver symbol

The IR receiver symbol is drawn as a compact 3-pin block representing the physical module — typically a 3-leg TO-92-like package with a dark (IR-filtering) front face or a right-angle PCB-mount module. The three terminals are labelled OUT (signal output, left pin), GND (ground, centre pin), and VCC (supply, right pin) — matching the TSOP1738 pin order when viewed from the front. In simplified schematics, it may appear as a diode symbol with a wavelength annotation (λ) indicating light sensitivity.

Function and usage boundary

The IR receiver module performs four functions in a single package: the integral IR photodiode converts incoming 940 nm infrared photons to a small photocurrent; a transimpedance pre-amplifier converts and amplifies the photocurrent; an automatic gain control (AGC) circuit adapts to varying signal strengths; and a bandpass filter rejects ambient light interference and selects only signals modulated at the designed carrier frequency (36, 38, or 40 kHz). The demodulated output is an active-low logic signal — it idles high and goes low during burst reception — that a microcontroller decodes to recover the transmitted button code.

Standards: IEC vs ANSI

IEC 60617	IEC 60617 does not define a unique symbol for integrated IR receiver modules; they are represented as general electronic device blocks per IEC 60617-02 functional block conventions. The photodetector portion follows IEC 60617-05 (semiconductor devices — photodiode symbol with sensitivity direction arrow).
ANSI/IEEE 315	ANSI/IEEE 315-1975 represents photosensitive semiconductor devices with a diode symbol with arrows indicating received light. An integrated IR receiver module is treated as a functional block with labelled terminals. The component designator is U (integrated circuit) or D (diode/photodetector) depending on the schematic convention.
Key difference	IEC and ANSI/IEEE both use the photodiode symbol or a functional block rectangle for IR receivers. The pin labelling convention (OUT, GND, VCC) is determined by the device manufacturer rather than an IEC/ANSI standard, as IR receiver modules are proprietary components not covered by a specific symbol standard.

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Logical terminals

Logical ID	Editor terminal name
out	OUT
gnd	GND
vcc	VCC

Where the IR Receiver symbol is used

TV, set-top box, and consumer electronics remote control reception: TSOP or VS1838B module receives NEC-protocol or RC5-protocol commands from a handheld IR remote, decoded by the system MCU to adjust volume, channel, and input source
Arduino and Raspberry Pi IR remote control decoder: 3-pin IR receiver module connected to a microcontroller GPIO enables the board to receive commands from any IR remote, decoded by IRremote or LIRC software libraries
Smart home IR blaster/receiver: IR receiver captures commands from an existing remote control, stores them in a microcontroller, and retransmits via an IR LED to control non-smart appliances such as air conditioners and older TVs
Infrared data communication (IrDA): front-panel IR transceiver module on portable devices and printers for short-range, line-of-sight serial data communication per the IrDA standard
Robot obstacle avoidance and line following: paired IR transmitter and receiver modules detect surface reflectance differences for line-following robots, or detect proximity of obstacles
Industrial machine position sensing: retroreflective IR sensor pair (transmitter + receiver) detects part presence, conveyor item counting, or rotation speed via interrupted IR beam

Key facts

The IR Receiver symbol has three terminals: OUT (demodulated active-low logic output), GND (ground), and VCC (2.5–5.5 V supply) — matching the physical pinout of TSOP1738 and VS1838B modules when viewed from the front.
IR receiver modules demodulate 38 kHz carrier-frequency modulated infrared signals (940 nm wavelength), outputting an active-low logic pulse train representing the remote control data.
The output signal idles HIGH and goes LOW during data burst reception; a microcontroller measures the pulse widths to decode NEC, RC5, RC6, or proprietary remote control protocols.
The most common carrier frequencies are 38 kHz (NEC protocol, used by most consumer electronics) and 36 kHz (RC5 protocol, used by Philips/Marantz equipment).
A decoupling capacitor combination — 100 nF ceramic in parallel with 4.7 µF electrolytic — on the VCC pin is essential to prevent supply ripple from causing the receiver's AGC to mis-interpret noise as valid signals.
Typical reception distance for a TSOP1738 is 10–15 m in line-of-sight conditions; reception is degraded by strong ambient light, IR-opaque obstacles, or mounting angle beyond the ±45° half-angle specification.
In ANSI/IEEE 315 schematics, the IR receiver module is designated U (integrated circuit) or D (photodetector); in IEC-based drawings it is typically labelled U or B (transducer/sensor).
The IR receiver module is distinct from a raw IR photodiode: the module includes AGC, bandpass filtering, and output buffering, so it outputs a clean digital signal directly readable by a microcontroller without external demodulation circuitry.

Frequently asked questions

What does the IR receiver symbol mean in a schematic?

The IR receiver symbol represents an integrated infrared demodulator module that detects modulated IR signals from a remote control handset and outputs a demodulated digital pulse train. It has three terminals: OUT (active-low digital output), GND (ground), and VCC (power supply), and connects directly to a microcontroller GPIO or interrupt pin.

What does the IR receiver symbol look like?

The IR receiver symbol is a compact 3-pin block labelled 'IR Receiver' or with the part number (TSOP1738, VS1838B). The three terminals are OUT (left), GND (centre), and VCC (right), matching the physical device pinout. In some schematics it may be drawn as a photodiode symbol with arrows indicating received light and separate labels for the supply and output terminals.

What frequency does an IR receiver work at?

Most IR receiver modules are designed for a 38 kHz carrier frequency, which is used by the NEC protocol (the most common IR remote control standard worldwide). RC5 protocol (Philips/Marantz) uses 36 kHz; RC6 uses 36 kHz; some manufacturers use 40 kHz. The carrier frequency must match between the IR transmitter (remote) and the receiver module for reliable detection.

What voltage does an IR receiver module operate at?

Most IR receiver modules, including the TSOP1738 and VS1838B, operate from 2.5 V to 5.5 V DC. This makes them compatible with both 5 V Arduino/AVR microcontroller boards and 3.3 V ARM-based boards (Raspberry Pi, ESP32, STM32) without the need for level shifting.

How does the IR receiver output signal work?

The IR receiver output is active-low: it idles in the HIGH state (close to VCC) and transitions LOW when a burst of 38 kHz modulated IR light is detected. This produces a pulse pattern corresponding to the remote control protocol data. A microcontroller measures the duration of these HIGH and LOW pulses to decode the button code being transmitted.

What standard defines the IR receiver symbol?

There is no specific IEC or ANSI standard symbol for an integrated IR receiver module. IEC 60617-05 defines the photodiode symbol (used for the sensing element inside the module), and IEC 60617-02 defines functional block symbols. In schematics, the IR receiver is treated as a labelled 3-pin component block; the designator is U (IC) or D (photodetector) depending on the schematic convention.

Why does the IR receiver need a decoupling capacitor?

The IR receiver module's internal AGC (automatic gain control) circuit is sensitive to supply voltage fluctuations. Power supply ripple or noise can be misinterpreted by the AGC as valid 38 kHz IR signals, causing spurious output pulses. A 100 nF ceramic capacitor (for high-frequency noise) in parallel with a 4.7 µF electrolytic capacitor (for lower-frequency ripple) placed close to the VCC pin suppresses these disturbances and ensures reliable reception.

Related symbols

Physical breadboard, PCB, and panel mapping

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