How to choose the right components for the following project?

[JUAK]

Hello,
Im doing a resonant inductive coupling system as my project.
A transformer used to step down the wall outlet (230V/50Hz) to 24V @ 3A, to be used as the input to a rectification circuit consisting of bridge rectifier and a filter cap.
after that, there is a crystal oscillator circuit operation at 13.56 MHz followed by class B (N-P) mosfet power amplifier to amplify the oscillator output to the transmission coil.

oscillator circuit diagram can be shown at the following link:
**broken link removed**

*( The output of the oscillator is not directly connected to the transistor gates, an additional operational amplifier were used to reduce the crossover distortions. A negative feedback loop is connected the output of the transistors to the inverting terminal of the op-amp, the oscillator output connected the non-inverting terminal and the output of the op-amp is connecting the transistor gates).

this is simply, how my transmission circuit would look like.
my problem is, how to get the right value of the components that operates at the specified frequency and also taking into account the voltage & current feeding the circuit, such as P and N mosfet Transistors, op-amp, and the IC Hex-inverter which completes the oscillator circuit.

Your responds will be much appreciated..
Thank you..

 

[audioguru]

Your oscillator circuit uses an ordinary Cmos inverter (but your transformer voltage is much too high) that has a maximum frequency of about 5MHz. Maybe a Cmos high-speed 74HCxxx inverter can be used which has a maximum frequency of about 50MHz. Its output is a square-wave with no crossover distortion.
The datasheets for a crystal and for an inverter have schematics of the oscillator and have suggested parts values.

You might not find an opamp that works at your high frequency.

 

[JUAK]

i appreciate ur fast respond..
The transformer has a center tap secondary, so 12 V also could be used.
But may i know why 24V is considered too high,plz?

as far as i searched, epically at high frequencies push-pull mosfet is not recommended to work on its won, due to the undesired crossover distortions.
any suggestions on how to reduce the crossover distortion generated by the transistors?
and how to choose the right value of the mosfet transistors that work at the mentioned input values?

thx..

 

[audioguru]

You did not say the 24VAC had a center-tap so when rectified and filtered it produces +32V.
The IC needs only 5V.

Now that you admit there is a center-tap then the rectified and filtered supply will produce +16V which is also much too high.

Mosfets are usually not used in audio power amplifiers. They are used as PWM switches.

 

[JUAK]

voltage divider rule, would it work here to reduce the input voltage?
so you think BJT transistors are better to be used rather than Mosfet?

 

[audioguru]

A voltage divider is used to provide a reference voltage to a point in aq circuit that has very low current.
BJTs are used in nearly all audio power amplifiers and perform very well.
Mosfets are used as switches.

 

[JUAK]

Thank you for your time..