# Laser Audio Transmitter - Need substitutes

#### livelongpranav

Joined Oct 18, 2017
19
Hey everyone!

I'm building a laser audio transmitter that uses amplitude modulation to transmit audio via a 5mW laser beam.

The transmitter uses a microphone, an operational amplifier (to modulate the signal if I'm not wrong) and a 5mW laser diode.

The receiver uses a phototransistor and a one watt amplifier along with a 8 ohm speaker to play the audio.

Schematic diagrams are attached. I earlier planned to make the transmitter using a 1000:8 audio output transformer instead of the Op-Amp, but couldn't find it anywhere in India, so I switched to this circuit.

Now the problem is, I am still unable to find the two most critical components - the 7611 CMOS Operational Amplifier and the TDA7205 1W Amplifier.

India has some quite good online component stores, and though they have most of the components, unfortunately these two are not available.

So this is what I need help with:

-Can I replace the 1W amplifier and the Op-Amp with some other model number (like 547 and 548 transistors are generally interchangeable) available here?

These are the Op-Amps available in India: 741 IC, ICL7650S IC, LF412 IC, LM346N, MC3403, NE5532, OP177, TL082.

These are the amplifier ICs available in India: A7840, AD620, AD623, CA3102E, CD4440, LF398, LF412, LM380N.

-Can you guys suggest me something cool and maybe useful to build? If I won't be able to make this due to lack of components, maybe I can build some other cool circuit. Any ideas?

I'm pretty new to electronics and I'm really excited for this project.Thank you everyone.

PS: Mouser, Digikey etc are not an option to get the components as the component price is $2-3 and their shipping and handling charge is$50+!

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