SPDT Analog Switch
Single-pole double-throw analog switching for signal routing.
What is it?
An SPDT (Single-Pole Double-Throw) analog switch is an IC with one common terminal and two switched terminals, logic input selects which switched terminal connects to the common. Unlike a logic gate, SPDT switches pass analog signals bidirectionally (input or output, either way). Used wherever you need to route one signal between two destinations or pick one of two sources to feed downstream.
When do you need it?
- Routing one ADC input between two sensors.
- Selecting between two audio sources to feed an amplifier.
- Switching crystal oscillator outputs to different paths.
- Antenna selection (RF SPDT for 2.4 / 5 GHz dual-band).
- Bypassing a circuit element (e.g., enabling/disabling a filter).
How to pick the right one
- Bandwidth
- How fast a signal can pass through. Standard analog SPDTs: 50-100 MHz. RF-optimised: GHz range.
- RON (on-state resistance)
- Lower = less signal attenuation and lower noise. <1 Ω for high-fidelity audio.
- RON flatness
- How constant RON is across signal voltage. Important for low-distortion analog routing.
- Off-isolation
- How well the off-channel is isolated from the on-channel. Critical for adjacent-channel interference in RF / video.
- VCC range
- Single-supply (1.8-5.5 V common) or dual-supply for bipolar signal handling.
What Magnias offers
Three SPDT switches: MI3157A-TW (single SPDT, 1.5-5.5 V, 9.5 Ω typical, 600 MHz bandwidth, SOT363) for audio, video, UART and USB 2.0 signals; MI3204C-T16 (quad SPDT, 2.3-5.5 V, 10 Ω, 0.2% THD, TSSOP-16L) for audio and video routing; and MI6603S-TW (RF SPDT antenna switch for 1.0-3.0 GHz, 0.30 dB insertion loss and 23 dB isolation at 2.45 GHz, SOT363) for WLAN and Bluetooth.