In the world of electronics, isolation is paramount. Whether you are designing a switched-mode power supply (SMPS), a microcontroller interface for industrial machinery, or a safety circuit for a medical device, the need to separate high-voltage domains from low-voltage logic is non-negotiable. The unsung hero of this task is the optocoupler (also known as an optoisolator).
Among the sea of component numbers, "1458" appears frequently in search queries and parts lists. However, there is a critical distinction to make immediately: The "1458" is most famously a dual operational amplifier (specifically the MC1458 or LM1458), not a standard optocoupler. This confusion is common. Therefore, this article serves two purposes:
By the end of this guide, you will know exactly how to find, read, and apply the correct datasheet for your isolation needs. 1458 optocoupler datasheet
Assuming your "1458 optocoupler" is a standard DIP-6, here is the pinout (identical to 4N35, PC817, and most general-purpose types):
Top View (Notch facing left or up)
---- Notch ----
| 1 o o 6 |
| 2 o o 5 |
| 3 o o 4 |
------------
Typical Wiring for Logic Isolation:
This section provides the "map" for your circuit design.
A true datasheet wizard reads the graphs, not just the tables. For your 1458-style optocoupler, focus on these three graphs: In the world of electronics, isolation is paramount
The 1458 is a single-channel, phototransistor output optocoupler designed for electrical isolation between input and output circuits. It consists of a Gallium Arsenide (GaAs) infrared emitting diode optically coupled to a silicon NPN phototransistor, packaged in a standard 6-pin DIP (Dual In-line Package).
| Parameter | Min | Typ | Max | Unit | |-----------|-----|-----|-----|------| | Input forward current | 1 | 10 | 20 | mA | | Supply voltage (output) | - | 5 | 24 | V | | Collector load resistance | 1 | 10 | 100 | kΩ | | Ambient temperature | -25 | 25 | 85 | °C | By the end of this guide, you will
The component designation "1458" presents a significant ambiguity in electronics engineering, as it is historically associated with the LM1458 dual operational amplifier rather than any optocoupler. This paper first resolves this nomenclature conflict, then establishes a generalized methodology for interpreting optocoupler datasheets. Using the widely recognized 4N35 optocoupler as a representative case study, we analyze key parameters including Current Transfer Ratio (CTR), isolation voltage, rise time, and forward voltage. The paper concludes with a decision matrix for selecting optocouplers in common applications such as microcontroller isolation and solid-state relay driving.
Microcontroller to 24V PLC Input Isolation: