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Topic: Using a two transistor NAND gate as a IR LED modulator (PWM + I/O) (Read 1 time) previous topic - next topic

BlueBill

It might already have been done, it might be the wrong way of doing it but is anyone modulating IR LEDs (for remote control) using a two transistor NAND gate.
The idea is setting one output pin (A) for PWM @ 38kHz ~ 33% duty (common for IR) and another other pin (B) just clocking out the data.
The NAND gate would be similar to this.


Comments.
Bill

Grumpy_Mike

It is a technique called a totom pole, used in old logic gates. It works if you want to do it that way. Note you get two times the Vsat voltage so the swing is a bit limited.

pwillard

Technically... the official "totem pole" output would send the signal out between the lower transistor's collector and the upper transistor's emitter.  I believe that this is the scenario where you get more limited swing... a bit less in your case when using the upper transistors collector.

BlueBill

Thanks, it seems like a cheap & cheerful solution. I'll give it a shot.
Bill

dhenry

You can use one transistor for that - one signal to the base and another to the emitter.


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