solderic.com The 4N35 and 6N137 are both optocouplers used for electrical isolation, with the 4N35 featuring a slower transistor output suitable for low-speed applications and the 6N137 providing a high-speed open-collector output ideal for fast digital communication. To understand which component best fits your project's speed and isolation needs, continue reading the detailed comparison in this article.
Comparison Table
| Feature | 4N35 | 6N137 |
|---|---|---|
| Type | Phototransistor Optocoupler | High-Speed Photodarlington Optocoupler |
| Speed | Standard (up to 5 kHz) | High (up to 10 Mbps) |
| Isolation Voltage | 5000 Vrms | 5000 Vrms |
| Propagation Delay | ~5 us | ~75 ns |
| Output Type | Phototransistor | Open Collector Transistor |
| Input Forward Current | 10 mA typical | 10 mA typical |
| Supply Voltage | None (input LED biased) | 5 V required for output |
| Application | General isolation, slow signals | High-speed digital isolator |
Introduction to 4N35 and 6N137 Optocouplers
The 4N35 is a widely used optocoupler featuring a phototransistor output, commonly employed for low-speed signal isolation with typical CTR (Current Transfer Ratio) ranging from 100% to 600%. The 6N137, by contrast, is a high-speed optocoupler with a photodiode and transistor output, designed for data rates up to 10 Mbps and featuring a typical propagation delay of under 100 ns. Both devices serve to provide electrical isolation between high-voltage and low-voltage circuits but differ significantly in speed and output configuration, catering to distinct application requirements in digital communication and signal isolation.
Key Features Comparison: 4N35 vs 6N137
The 4N35 optocoupler features a phototransistor output with typical CTR (Current Transfer Ratio) ranging from 50% to 600%, making it suitable for low-speed, general-purpose isolation applications. In contrast, the 6N137 employs a high-speed photodiode and Schmitt trigger output, achieving propagation delays as low as 35 ns and data rates up to 10 Mbps, ideal for high-speed digital isolations. The 6N137's guaranteed minimum CTR and improved noise immunity outperform the 4N35 in precision and speed-critical interfacing tasks.
Electrical Characteristics Overview
The 4N35 is a widely used optocoupler featuring a phototransistor output with input current typically around 10 mA and CTR (Current Transfer Ratio) ranging from 20% to 300%, operating at a CTR of about 50% under normal conditions. The 6N137, on the other hand, is a high-speed optocoupler with a photodiode and a high-gain transistor output designed for fast switching, offering propagation delays as low as 35 ns and a higher isolation voltage of 5000 Vrms. While the 4N35 suits general-purpose isolation needs with slower speed and moderate CTR, the 6N137 excels in digital communication applications demanding high-speed data transfer and low input current operation (~10 mA typical), with a bandwidth up to 1 Mbps.
Speed and Performance Differences
The 6N137 offers significantly faster switching speeds compared to the 4N35, with propagation delays typically around 10 nanoseconds versus the 4N35's 3.5 microseconds. This speed advantage makes the 6N137 ideal for high-speed digital communication and data isolation applications where rapid response is crucial. Your choice depends on whether ultra-fast performance or cost-effective general isolation is the priority.
Common Applications in Electronics
The 4N35 optocoupler is frequently used for low-speed signal isolation in applications such as switching power supplies, microcontroller interfaces, and basic digital communication. The 6N137, known for its high-speed operation up to 10 Mbps, is ideal for fast data transmission tasks like high-speed UART communication, RS-232 line drivers, and isolating clock signals in digital systems. Understanding your application's speed requirements and signal types helps determine whether the 4N35's versatility or the 6N137's rapid response is the best fit.
Advantages of 4N35 in Circuit Design
The 4N35 optocoupler offers advantages in circuit design with its compact phototransistor output, providing reliable isolation and low power consumption suitable for general-purpose applications. Its slower switching speed compared to the 6N137 is beneficial in reducing high-frequency noise and electromagnetic interference in sensitive analog circuits. The 4N35's widespread availability and cost-effectiveness make it a preferred choice for simple isolation tasks in consumer electronics and industrial control systems.
Benefits of Using 6N137 for High-Speed Data
The 6N137 optocoupler offers superior high-speed data transmission with propagation delays as low as 35 ns, making it ideal for applications requiring fast and precise signal isolation. Its high common-mode transient immunity up to 25 kV/us enhances noise rejection in industrial environments. Compared to the 4N35, the 6N137 provides enhanced switching speeds and improved data integrity in digital communication systems.
Pin Configuration and Package Types
The 4N35 optocoupler typically features a 6-pin dual in-line package (DIP) suited for basic isolation tasks, with pins dedicated to the infrared LED input and phototransistor output. In contrast, the 6N137 uses an 8-pin small-outline integrated circuit (SOIC) or DIP package, offering an improved fast response with a photodiode and a Schmitt trigger output stage, making it suitable for high-speed digital signal isolation. Your choice depends on the required interface; 4N35 fits low-speed, simpler designs, while 6N137 excels in faster, more complex applications demanding precise pin configurations for advanced signal integrity.
Reliability and Noise Immunity Analysis
The 4N35 optocoupler exhibits moderate noise immunity with a typical CTR (current transfer ratio) range of 100-300%, making it suitable for low-speed applications where reliability is essential but noise levels are manageable. The 6N137 provides superior noise immunity and high-speed performance, featuring a propagation delay of less than 75 ns and low input-output coupling capacitance, which enhances reliability in high-speed digital isolation tasks. For applications demanding robust noise rejection and consistent signal integrity, the 6N137 is the preferred choice due to its advanced construction and enhanced transient immunity.
Selecting the Right Optocoupler: 4N35 or 6N137
Choosing between the 4N35 and 6N137 optocouplers depends on your circuit requirements for speed and isolation. The 4N35 offers moderate switching speeds up to 5 kHz with high isolation voltage of 5000 Vrms, making it ideal for low-frequency signal isolation. The 6N137 supports high-speed data transfer up to 10 Mbps with a propagation delay as low as 75 ns, suitable for fast digital communication in your design.
4N35 vs 6N137 Infographic
