NEW !!! Full differential PI front end.

language difficulty

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Eğer bunu anlamak ... çok faydalı olduğunu

This was intended as an English Language website. There are some inconsiderate, self important people who disrupt or hijack the flow of ideas by using Arabic or other obscure languages to carry on back-channel conversations that 99% of readers on this forum will never understand.

If you would at least tell the others here what language you are using we might be able to figure out would you are saying.

If we would all try to stick to English then there would be a single language for everyone to learn instead of myriad of languages.

If your messages are private, then why don't you use PM instead of intruding on the others. Take it somewhere else.

[moodz]

Decay curve measured at point B on schematic ... pulse set to 100 uS

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Eğer bunu anlamak ... çok faydalı olduğunu

[moodz]

Balun core specifications

• MATERIAL 26 Permeability 75
• DC to 1 MHz (Low 'Q')
• Color - Yellow & White
  
  Amidon type no T106-26
  outer diameter = 1.060
  inner diameter = .570
  height = .437
  uH / 100 turns = 900

merhaba aziz abi

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[moodz]

Updated schem.

Minor changes ... ( for Aziz )

+Diff amp resistor to gnd.

+Tank cap.

Have not tested circuit with added resistor.

[moodz]

Additional component values ...

Oh yeah ...

the diodes are 1N5822 schottky

The MOSFET is IRFP460

Cheers again ...

moodz

[moodz]

Hi Aziz,
thanks for your comment ... you could be right ... I have only really shown the amp as an example ... the key part is the differential signal feeding the amp.

Note I have also not shown the tank capacitor on the V+ supply ( 4700 uF )

Also V+ for the amp would not be the same as the balanced Tx circuit.

On my lashup the Tx supply is +5 volts and the amp is +16 volts.

There is probably alot that could be done to optimise this circuit but I am confident that this may have some impact on the thinking of designers of PI frontends for future designs.

Cheers ...

[Aziz]

Hi Paul,

this idea is looking really very interesting. If I look into the schematics, I am missing a resistor from the non-inverting op-amp input (pin 3) to ground (1MO). Then a fully difference amplifier is implemented.
The difference amplifier has a quite low input impedance. So other low noise types of op-amps could be used anyway.
Correct me, when I am wrong.
Regards,
Aziz

[moodz]

I was in another thread here where I posed a question as to why PI frontends seem to be unbalanced hence all the problems with noise and front end amplifier design. One side of the coil is basically connected to signal ground and the other to a high gain amp and worse it is a DC amp requiring careful adjustment of an offset voltage.

Well I will have to eat my words ... because I have just knocked up the following circuit and hoohah ... it works like a beauty .

Note in the schem below there is no DC offset adjustment. This circuit worked straight up with the component values listed.

I only thought of this and knocked it up in the last hour or so ... ie Version 1.00

If you look at points A to ground then B to ground with a scope you will see the high voltage spike indicating that the coil is no longer unbalanced ( ie grounded on one side. ) thanks to the balun.

No need to thank me ... beer is fine

With out further ado ... the circuit.



... and the BALUN ... the rest of the components you've seen already.