Hi All,
I am in the process of designing a PWM comms system that drives a LASER light with the receiver being an LDR circuit some distance away. I am having a bit of trouble getting a reliable triangle wave output from an oscillator circuit that I am using.
The circuit
The formula
My circuit interface requirements are thus,
The final PWM output must have a 3vp-p output to conform to the LASER operating voltage. The Triangle Wave must be around 10kHz in frequency, this meets the requirement of the reference wave being at least double the highest frequency of the information (3400Hz for voice). I'm not sure what the Vpp requirements of the triangle wave should be in order to match this circuit. I'm not sure if its even relevant, it will be summed with the modulation waveform using a circuit I am yet to determine (perhaps a simple resistive network using DC blocking capacitor at output of oscillator).
Basically, the problem I am having is choosing appropriate resistance and capacitance values. I have achieved a 12kHz output on a breadboard but the triangle wave is distorted during the negative going ramp. I am not set on this circuit so if you know of any alternatives that are simpler please suggest them.
Any advice appreciated.
Cheers,
Rueffy.
I am in the process of designing a PWM comms system that drives a LASER light with the receiver being an LDR circuit some distance away. I am having a bit of trouble getting a reliable triangle wave output from an oscillator circuit that I am using.
The circuit
The formula
My circuit interface requirements are thus,
The final PWM output must have a 3vp-p output to conform to the LASER operating voltage. The Triangle Wave must be around 10kHz in frequency, this meets the requirement of the reference wave being at least double the highest frequency of the information (3400Hz for voice). I'm not sure what the Vpp requirements of the triangle wave should be in order to match this circuit. I'm not sure if its even relevant, it will be summed with the modulation waveform using a circuit I am yet to determine (perhaps a simple resistive network using DC blocking capacitor at output of oscillator).
Basically, the problem I am having is choosing appropriate resistance and capacitance values. I have achieved a 12kHz output on a breadboard but the triangle wave is distorted during the negative going ramp. I am not set on this circuit so if you know of any alternatives that are simpler please suggest them.
Any advice appreciated.
Cheers,
Rueffy.