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Wireless infrared headphone transmitter

2016-02-13 17:28  
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 This article describes a wireless infrared headphone transmitter. The principle is simple there, we recommend that combine text carefully read the complete schematic. Figure: Audio input from PL1 frequency modulates the VCO section of a 4046 PLL chip. The VCO output drives Q1, a switching transistor. Q1 drives two IR LEDs. The signal produced is around 100 kHz, FM carrier VCO sensitivity is around 7.5 kHz / V. this circuit is an important component is 2N2222A. For you to better grasp the principle, then we briefly 2N2222A . The 2N2222A is silicon planar epitaxial NPN transistors in Jedec TO-39 (for 2N2219A) and in Jedec TO-18 (for 2N2222A) metal case. They are designed for high speed switching application at collector current up to 500mA, and feature useful current gain over a wide range of collector current, low leakage currents and low saturation voltage. to better grasp this principle, it is recommended to read several times on this principle.

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