RF-rated solid-state relay with 12.5 Ohm channel resistance
The Panasonic AQY221N2TW is an SPST-NO (1 Form A) solid-state relay from the PhotoMOS™ AQY2 series, designed for signal-level switching where a clean, bounce-free contact closure matters more than a mechanical relay's contact rating. The output is specified for AC, DC, and RF signals, meaning the internal MOSFET pair switches bipolar signals without a polarity constraint — useful for audio crosspoints, multiplexing sensor outputs, or bypassing a gain stage in a signal chain.
1.14 V logic drive and surface-mount footprint
The input LED turns on at 1.14 VDC — this is the guaranteed turn-on threshold, not a typical. A 1.2 V or 1.8 V logic rail drives it directly without a series resistor calculation; the input current is set by the external current-limiting resistor to the LED's absolute-max rating, which is 50 mA continuous. Housed in a 4-SMD package (1.80 mm body height) also known as 4-VSSOP, the footprint occupies about 3.5 mm × 4.5 mm on the board. The SMD (SMT) Tab termination is the standard gull-wing profile — no exposed pad to solder, so the reflow profile follows the standard JEDEC J-STD-020 for a small-outline package. The 4-pin layout is the classic PhotoMOS pinout: pins 1 and 2 are the LED input (anode and cathode), pins 3 and 4 are the MOSFET output. Polarity on the output side does not matter for DC or AC — the back-to-back MOSFETs block both directions when off and conduct both when on.
The PhotoMOS AQY2 series is a mature, catalog-maintained line, so the risk of an unplanned EOL notice in the next 12–18 months is low for a standard order code. The base product number AQY221 covers multiple variants (different package options, tape-and-reel quantities); the N2TW suffix specifically denotes the 4-VSSOP package on tape-and-reel. If the BOM calls for the same die in a different package, the AQY221 base number is the cross-reference anchor.