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[on:]

Hi,

i'm working on a simple small signal amplifier as my bachelor thesis. The goal is be the pcb.
During the presentation i would like to demonstrate the functioning by using arduino but i need
a pure sine wave signal to feed the amplifier.
I studied the theory abt radio transmissions, and correct me if i'm wrong, the AM radio receiver should
incorporate a frequency variable device.
The question is: can i rip off that device (if there is any) from a AM receiver and use it as my sine wave generator? 

[Reply #1 on:]

Hi,

i'm working on a simple small signal amplifier as my bachelor thesis. The goal is be the pcb.
During the presentation i would like to demonstrate the functioning by using arduino but i need
a pure sine wave signal to feed the amplifier.
I studied the theory abt radio transmissions, and correct me if i'm wrong, the AM radio receiver should
incorporate a frequency variable device.
The question is: can i rip off that device (if there is any) from a AM receiver and use it as my sine wave generator?  

Not likely, modern AM radios use 'local' oscillator that is intergrated along with most of the other AM radio functions into a single chip. Plus the frequency of the AM local oscillator is well above the hearing range of humans.

It's not too hard to generate a sine wave from a Arduino timer output and pass it through a simple resistor/capacitor low pass filter. Check out the Tone library for creating audio frequencies with an arduino.

[Reply #2 on:]

No.
Look in the playground for an arduino sin wave generator.

[Reply #3 on:]

Thanks. I'll take a look to both

[Reply #4 on:]

Hi,
It might be overkill and/or not fast enough for your needs, but I posted an approach a little while ago for an arbitrary amplitude + arbitrary waveform generator implemented purely in software: http://arduino.cc/forum/index.php/topic,63604.0.html .

For a one-off project, it's probably easier to follow retrolefty's suggestion of generating a squarewave (tone()) and filtering it. VCO (voltage controlled oscillator) circuits are fun to play with too if you have the time; this may give you a more consistent signal over the entire audio frequency range (won't have to worry about rolloff from the squarewave-filter).

[Reply #5 on:]

What should be the frequency range of the sine generator?

[Reply #6 on:]

i'm using the LM318 and a bilateral current pump configuration.
The bandwidth is 1MHz, but since i need the VOC just for a little dimostration, some kHz are also good
thank you