4N35S-TA1

4N35S-TA1 is a variant of the classic 4N35 optocoupler (photocoupler). It contains an infrared LED input and a phototransistor output with galvanic isolation between the input and output sides, so signals can be transferred without a direct electrical connection. This provides protection from high voltages, noise, and transients, and enables level shifting between circuits.
The S-TA1 suffix typically indicates a specific packaging, temperature grade, or vendor variant; exact electrical specs (CTR, isolation voltage, speed) vary by lot, so check the datasheet for precise values.
How it’s used: drive the input LED with a current-limited signal; on the output side, use the transistor as a switch or small-signal amplifier with an external pull-up/down resistor, keeping the isolated side separated from the input.
Key specs to review: isolation voltage (several kV), CTR (depends on If and temperature), maximum input/output currents, and response time. Applications: microcontroller interfaces, safety/isolation, noise immunity, and level shifting.

Direct equivalents (same function: phototransistor optocoupler) include: 4N25, 4N26, 4N27. Comparable substitutes from other manufacturers: PC817 / EL817, MCT2E, and generic phototransistor optocouplers. Verify CTR, isolation voltage, speed, package and pinout against the 4N35S‑TA1 datasheet before replacing.

Here are the key features of 4N35S-TA1 (a 4N35 family optocoupler variant):
- 6-pin DIP optocoupler with LED input and NPN phototransistor output.
- Input side: infrared LED; typical forward current ratings up to about 60 mA; Vf ≈ 1.2 V at 20 mA.
- Output side: NPN phototransistor; current transfer ratio (CTR) varies widely with IF, VCE, and temperature.
- Isolation: provides galvanic isolation between input and output, typically 5 kV RMS.
- Output configuration: open-collector style; use a pull-up resistor for logic signals (TTL/CMOS compatible with proper CTR).
- Package variant: 4N35S-TA1 in a standard 6-pin package (S/TA1 packaging variant; Pb-free often available).
- Suitable for signal isolation, level shifting, and interfacing microcontrollers to higher-voltage circuits.
- Slow compared to modern high-speed optocouplers; intended for general-purpose, low-to-moderate speed switching.

The 4N35S‑TA1 is a 6‑pin phototransistor optocoupler. Typical pin functions (DIP‑6 numbering) are:
- Pin 1: LED Anode
- Pin 2: LED Cathode
- Pin 3: No connection (NC)
- Pin 4: Phototransistor Emitter
- Pin 5: Phototransistor Collector
- Pin 6: Phototransistor Base (optional access for biasing/response control)
Operation: an input LED (pins 1–2) optically drives an output NPN phototransistor (pins 4–5) providing electrical isolation; pin 6 lets you externally bias the transistor to change sensitivity or switching characteristics.

Manufacturer: Vishay Intertechnology.
What kind of company: A global electronics components company that designs and manufactures semiconductors and passive components, including optocouplers like the 4N35S-TA1.

4N35S-TA1 is a phototransistor optocoupler used for galvanic isolation. Typical applications:
- Isolate microcontroller/PLC logic from high-voltage/noisy power circuits.
- Drive small relays or external transistor stages via the optocoupler.
- Signal conditioning, level shifting, and noise suppression with isolation.
- Safety interlocks and alarm circuits in industrial/medical equipment.
- Isolated sensor interfaces and data links (low-speed signals, a few kHz).
Notes: provides isolation up to about 5 kV RMS (per datasheet) and is suited for low-speed, not high-speed data.

The 4N35S-TA1 is supplied in a 6‑pin plastic dual‑in‑line (PDIP/DIP‑6) through‑hole optocoupler package.