Signal Generation

[Bavananth]

Hi! I have a beeeg problem here.

Please kind enough to go through the pictures drawn down here.

When I apply A sinusoidal to that ferrite rod from a KENWOOD signal generator, my system works properly. but I have to use my own signal generator for the final system. I designed a one and It worked well. But the problem is when I apply it to the rod, the voltage drops.

I decided that the low reactant of the coil may be the reason. But why did it work with the signal generator? What shall I do to this problem? I'll update my test results. Please give some comments. (If you no anything about 8038 ICs,pls share that also)

 

[Bavananth]

I've forgotten to mention that in diagram 3 the point 1 shows a distorted/noise signal and point 2 shows a Sinusoidal.

 

[crutschow]

The signal generator probably has a 50 ohm output impedance. The 8083 is tested with 1k ohm output impedance. You need a buffer amplifier on the 8083 output to drive a low impedance load.

 

[Hero999]

Eventually, you've posted a picture and we can understand what you're doing!

So you want to build a 300kHz continious wave transmitter?

You don't need a linear amplifier, an RC filter or an 8038.

Just stick a capacitor in parallel with your ferrite rod coil and tune it to 300kHz. Feed it with a 300kHz squarewave using a MOSFET driven by the NE555 and it'll ring at 300kHz and produce a sinewave with very few harmonics.

I've done this before at 500kHz and it works perfectly.

 

[Bavananth]

Thank you so much! I have some English trouble in the reply. I don't know the way I Understood your system is correct or not. I have shown here how I understood your explanation.Is it correct?

 

[Bavananth]

LC oscillator

I hope LC oscillator would do my work.(I hope that is what you mentioned in your idea hero)

 

[audioguru]

Your receiving coil should also be tuned with a parallel capacitor.

Look at the datasheet for the very old 741 opamp:
1) Its output drops above only 9kHz.
2) At 300kHz its max gain is only about 3 when its load is 2k ohms or more.

 

[Hero999]

Just drive the MOSFET from the 555.

 

[Bavananth]

Thank you for your reply hHero, I have simulated your cct using Orcad. But It doesn't show me the desired output??? Any clues?

 

[Bavananth]

If you like pls go through the Orcad files folder given below.
Run the testma.dsn (schemetic 1,paGE 2) to get the above diagram

 

[Bavananth]

I have tried changing values for pulse width time, Frequency of mosfet driving pulse, Inductor values. But no change in the signal out

 

[Hero999]

The capacitor and inductor values need to give a resonant frequency close to 300kHz. For example if you set L to 820:mu:H and C to 330pF, the resonant frequency is 306kHz which should be near enough.

 

[Bavananth]

Whatever I do in the Orcad no change in the output. I think it has not been programmed for the resonant part. Anyway I have tried a loooooooot of ways to create AC from DC. Every think failed. Your model looked like some SMPS(those bucks booosts) stuff. So I thought It may work. Anyway I'm going to try your one practically. But While I was doing some Buck stuff in the orcad simulation worked. Thats why I wonder it fails now. If your one also fails I'm in trouble. May god find me some other way. thanks hero

 

[Bavananth]

Hi Hero, could you please explain me that how your system works such that it generates a sinusoidal? Any reference which could help me?

 

[Hero999]

The inductor and capacitor form a resonant tank circuit that rings if the pulses applied to the MOSFET's gate are the same frequency or a harmonic of the resonant frequency.

 

[Bavananth]

You mean some think like this? **broken link removed**

 

[Bavananth]

Thanks it is in " **broken link removed** " detail.
But it seems very hard to achieve it. Hmmmm.......!

 

[Bavananth]

Small correction

Hi Hero, I found out the diagram by randomly connecting components in Orcad Capture. So I hope this is what u've meant. Have a look at this thanks alot.

 

[Bavananth]

When adjusting Pulse time and Capacitor values I'm able to get a ALMOST STABLE signal. But the there is a voltage ripple. Have to check in the practical situation.

 

[Hero999]

You need to make sure the frequency of the pulses at the MOSFET's gate is 300kHz or a subharmonic of that, i.e. 150kHz, 75kHz etc.