Bipolar PI design

[Detectorist#1]

Hi algan,
The more real problem is not the using of strong MOS FET drivers. The real problem in this schematic is the find solution with symmetrical parameters of N-ch and P-ch switches if you want real good results. On the schematic of N@SKO information for the type of upper P-ch MOS FET is absent. It is not easy to find equal parameters for upper and down MOS FET switch.

[eduardo1979]

I totally agree. I share your opinion.

[Orbit]

I think that Nasko has a solution, if he put the circuit of the Mikron hybrid transmitter, then he also knows the upper pn mosfet .... The receiver would be more interesting than the transmitter..The end result of the device working well will not be only the transmitter and not the receiver... Surely there are many things for the final solution. So nothing special will be gained just by having a transmitter or receiver.

[algan]

The second picture posted by Nasko shows which components he uses in the circuit: IRF640 + IRF9640, but let's say that the IRF740 + IRF9642 are closer in characteristics.

[Altra]

I don't believe the Mikron circuit is pi. One of the power mosfets is always conducting, so there is no off period to the coil. The circuit looks like an adaption of the Whites DFX or VI3 continuous square wave TX's

[pechkata]

Hello Altra
How can we program a time slot?
How can we build this type - time slot?
Is there any way to do this?

[Altra]

In your three photos. I think you are confusing the Tx and demodulation signals. Carl's drawing shows the demodulators sampling during the halfsine. The I sample is taken during the complete HS period and the Q sample is inverted for the first 90 deg of the HS and alternated between pulses. In the hand drawing and Johnson patent those are the Tx signals and not the demodulators. To make all this happen you need to concentrate on programming micro processors and learn how to generate the timing signals. Carl's book has all the info you need for the rest. I use the IRF640, IXTP26P20 and a TC4428 driver for the TX. The IXTP26P20 is expensive and the ones from China are fake

[pechkata]

In your three photos. I think you are confusing the Tx and demodulation signals. Carl's drawing shows the demodulators sampling during the halfsine. The I sample is taken during the complete HS period and the Q sample is inverted for the first 90 deg of the HS and alternated between pulses. In the hand drawing and Johnson patent those are the Tx signals and not the demodulators. To make all this happen you need to concentrate on programming micro processors and learn how to generate the timing signals. Carl's book has all the info you need for the rest. I use the IRF640, IXTP26P20 and a TC4428 driver for the TX. The IXTP26P20 is expensive and the ones from China are fake

Hello Altra
Exactly about Johnson's patent - I want to build his Tx signals.
Not for demodulators.
Thanks for the encouragement.

Google doesn't translate correctly.

[Detectorist#1]

Hi Altra,
Do you really need in this design MOS FETs with so low Rds on? What is the inductance of your TX coil and TX max current?

[Carl-NC]

Hello Carl-NC
Thanks for the clarification.
What do we feed to the points?
What kind of impulse?
NCLK1
PCLK1
NCLK2
PCLK2

For the half-sine the TX clocks are identical to the bipolar PI:



For the Impulse waveform the TX clocks are this:

[Altra]

Hi Altra,
Do you really need in this design MOS FETs with so low Rds on? What is the inductance of your TX coil and TX max current?

It's not so much about low RDSon, but matching. Low RDSon has benefits. The best test is the flyback voltage comparison between n and p. Coils are 300-600uH, 1R or less. The tx current depends on a many factors like PW, Tx freq, Tx voltage coil resistance etc..

[N@SKO]

Mikron hybrid use IXTP26P20 too.Any idea how demodulator are controlled on it.

[Orbit]

There are smoke signals now all you need are hallucinogenic mushrooms and there you have it.

[Carl-NC]

You will never be able to match the P and N drive of a half-bridge driver. To get the Rds to match, the PMOS needs to be much larger than the NMOS. Then the parasitic capacitance of the PMOS will be much larger and the damping will be different for the P & N. You can fake it somewhat by adding series resistance or extra capacitance to the FETs.

[Altra]

Mikron hybrid use IXTP26P20 too.Any idea how demodulator are controlled on it.

No, I have only seen Youtube videos. But judging from the Tx circuit, it's probably more like a BBS detector than a PI?