[Moved] 2 MHz Power Oscillator

Hi guys!
I like to present a power oscillator working at around 2 MHz. It consists of a CMOS oscillator made from CD4069 IC. The inductor driven by Q7 is a loop shaped antenna. It has a diameter of about 5cm and has 15 turns. You may experiment with different antennas. Several Watts of output power may be obtained.



Greetings

Re: 2 MHz Power Oscillator

Your circuit may work but there are several problems with it.

First the third gate output should not be directly connected to transistor bases but via a current-limiting resistor.
Second, MOSFET gate should be protected from an overvoltage, typical maximum gate-source voltage is 6V.
Third, with the inductive load the MOSFET channel should be protected by a diode to prevent a breakdown.
Fourth, you can completely avoid the two BJTs and feed the MOSFET from the 3rd gate.


You may find soon that components will fail due to the missing above components.

Re: 2 MHz Power Oscillator

jiripolivka said:

Your circuit may work but there are several problems with it.

First the third gate output should not be directly connected to transistor bases but via a current-limiting resistor.
Second, MOSFET gate should be protected from an overvoltage, typical maximum gate-source voltage is 6V.
Third, with the inductive load the MOSFET channel should be protected by a diode to prevent a breakdown.
Fourth, you can completely avoid the two BJTs and feed the MOSFET from the 3rd gate.


You may find soon that components will fail due to the missing above components.

Click to expand...

1. The Gate current is limited by the saturated gain of BJT's (~20) and effective gate resistance will be the effective output impedance of CD4069 CMOS @8.2V ~300 Ohms divided by same gain of ~20 when saturated so Rg is effectively 15 Ohms.

2. This FET is rated for +/-20V abs max for Vgs

3. THis FET has internal body diode that clamps overshoot rated for 18A

4. Would this be effectively driving this FET Gate charge of ~35 nC from 300 Ohms (CD4xxx CMOS) at 6V?
if Ciss=1300pF then Rg*Ciss= 390ns which may distort the Vgs and increase dynamic power dissipation.

Looks ok to me. for transferring power to a similar coil over a gap of a few cm. max. Try it on a resonant coil with plastic cap in // but feed from receiver coil with a 1 or 2 turn tap to drive some 3W power LEDs back-to-back. The tap acts as a current step up transformer.