Learn about typical application circuits and selection recommendations of small signal transistors in smart speakers, such as switch control, level conversion, and LED driving.
Application Background
Smart speakers today offer a wide range of features beyond audio playback, including voice recognition, LED display control, USB wake-up, and relay triggering. Small signal transistors are widely used in these systems due to their low power consumption, high-speed switching capabilities, and low saturation voltage.
Application Circuits
On the smart speaker's main control board, NPN transistors are used to drive indicator LEDs, enable power chips, or switch low-current relays. Controlled via GPIOs from the MCU, these transistors ensure clean and reliable load switching.
Design Recommendations
It is recommended to operate these transistors within a VCE rating of 20V and a collector current of 100–200mA. Always use a base resistor to limit drive current. When cascaded with MOSFETs, they can control higher power stages. These transistors also work well in low-noise preamps and relay drivers.
Example Use
A smart speaker design employed small signal transistors to control LED indicators and microphone preamplifiers, enabling fast response and low standby power while enhancing voice detection accuracy.
Small signal transistor | LED control | Smart speaker switch driver | Audio preamp transistor
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