RFID amplifier question

[anad2560]

I am trying to build a 125 khz RFID reader unit and I have some question I hope someone could help me with. I need to maximise the read range of my unit but I am slightly constrained by how big I can make the reader coil. So, the only thing I can do is use a more powerful amplifier. I have been looking at the RFID reference design manual from Microchip and it has been a lot of help in designing my circuits. But I have one question regarding the interpretation of a paragraph in page 133 of the manual (https://ww1.microchip.com/downloads/en/DeviceDoc/51115F.pdf):

For long read-range applications, this power amplifier
circuit can be modified. Power MOSFETs may be used
instead of the bipolar transistors (2N2222). These
power MOSFETs can be driven by +24 VDC power
supply. A push-pull predriver can be added at the front
of the complementary circuit. This modification will
enhance the signal level of the carrier signal and the
read range of the ASK Reader.

Would I need to just replace the 2n22222 transistor with a mosfet and stick a push-pull driver in front of it?

I was also looking into circuits such as figure 2 shown here https://www.daycounter.com/Circuits/HV-MOSFET-Driver/HV-MOSFET-Driver.phtml

Also, another limitation I have is I need to be able to power my whole reader unit by using a 9V battery. Would it be useful to have a mosfet amplifier instead of the one given in the Microchip document?

Is there any other things I could do to increase the read range of the reader? Does anyone know of any sites with suitable example circuits I can play around with?

I should also mention that my whole design will need to be analogue as I will be doing some signal processing on the received tag signal.

Many thanks for reading.

 

[Diver300]

RFID is quite difficult to get working. Which type of RFID are you going to use?

If it is the simplest 125 kHz RFID, where the receive and transmit are on the same frequency, the limitation is generally on whether you can see the return signal from the RFID tag in the huge signal that you need to drive the coil.

Systems where the return signal is at a different frequency can get a better range.

Generally if you want a large range, you need a large reader coil and a large amount of power. If you have a small coil, the range will be small.

If you have to send data to the tag, it is usually necessary to make sure that the magnetic field from the coil turns on and off quite quickly, which limits the Q of the coils circuit that you can use. That in turn means that quite a lot of power is expended just keeping the magnetic field running. However, it might be possible to open the tuned circuit to stop the magnetic field quickly, keeping the energy in the capacitor, and allowing the field to be restarted quickly, even with a high Q coil.

 

[dougy83]

Would I need to just replace the 2n22222 transistor with a mosfet and stick a push-pull driver in front of it?

Both transistors (2n2222 & 2n2907) would be replaced. You will need some kind of driver circuit for the mosfets. Your 9V will not give as much range as the mentioned 24V either.