I'm trying to simulate and then build a circuit I found in a Vishay application note. In the schematic there is a 38 kHz sine wave going into a NAND gate. What options are there for generating a sine wave? Are there chip solutions? I think I want an actual sine wave and not a square wave from a 555 timer or something like that.

 

National Semiconductor AN-31:


If you integrate a square wave you get a triangle wave. If you integrate a triangle wave, you get a sine wave.

 

Why do you think you need a sinewave going to a digital gate?

 

I assumed it was a sin wave because of the drawing but looks like a sine wave into a gate is a bad bad idea...

 

I assumed it was a sin wave because of the drawing but looks like a sine wave into a gate is a bad bad idea...

A couple of points:

1. Looks more like a square wave with rounded edges.
2. 74xx parts usually have a power supply of +5 Volts and GROUND.
3. Sinewaves tend to have positive and negative peaks with an average value of 0 Volts aka GROUND.
4. The gate does not explicitly show the power (+5V) and GROUND (0 V) connections, but they damn skippy need to be there.

 

For driving an IR LED you do not need a sinewave. A square wave from a 555-timer circuit will work.

 

For driving an IR LED you do not need a sinewave. A square wave from a 555-timer circuit will work.

The CMOS 555 will make a much better gate driver than a 7400 NAND gate.

 

Don’t worry…if you drive an LED with a square wave it is pretty easy to turn it into a sine wave in the receiver/detector if it doesn’t happen automatically.

 

Note that the 38kHz for a remote control may require tweaking of a 555 astable to get it within the required frequency range.

 

Lets say I end up using something like the PWM pin of this PIC chip, datasheet here:
https://www.mouser.com/datasheet/2/268/PIC16_L_F15313_23_Data_Sheet_40001897C-1903366.pdf

The datasheet says it has a 10 bit resolution PWM. If I wanted to know that the fastest PWM signal (freq) I could send out using this PIC, what information should I look for on the datasheet that would tell me?