RFID Circuits
Last Updated on: Friday, August 29, 2008 02:33 PM
 

Circuits Designed by Dave Johnson, P.E.:

CMOS INVERTER 125KHz LC OSCILLATOR This circuit uses a single CMOS inverter to form a series resonant LD oscillator.   The values shown set the oscillation at about 125KHz but other frequencies are possible by changing the main LC values

CMOS INVERTERS FORM 125KHZ OSCILLATOR This circuit is similar to CMOS INVERTER 125KHz LC OSCILLATOR but inverts the LC components so the inductor is grounded.  Two inverters are needed to produce the needed oscillation.  Again, the values shown set the frequency at 125KHz but can be changed to produce other frequencies.

CMOS NAND GATE FORMS GATED 125KHZ OSCILLATOR This circuit is similar to CMOS INVERTER 125KHz LC OSCILLATOR but uses a NAND gate as an inverter.  The gate allows the oscillator to be gated on and off.  Again, the values shown set the frequency at 125KHz but can be changed to produce other frequencies.

MEDIUM POWER 125KHZ OSCILLATOR This circuit is similar to CMOS INVERTERS FORM 125KHZ OSCILLATOR  but adds more invertors in parallel to deliver more power.  The values shown are for 125KHz.

MEDIUM POWER 125KHZ OSCILLATOR This circuit is similar to MEDIUM POWER 125KHZ OSCILLATOR but adds even more inverters in parallel to deliver yet more power.  The values shown are for 125KHz.

MEDIUM POWER 125KHZ OSCILLATOR This circuit is similar to number 117 but adds more invertors in parallel to deliver more power.  The values shown are for 125KHz.

MEDIUM POWER 125KHZ OSCILLATOR This circuit is similar to number 119 but adds even more inverters in parallel to deliver yet more power.  The values shown are for 125KHz.

OPTICAL RFID TEST CIRCUIT I designed this test the concept of using light techniques to send identification data instead of RF. A more detailed discussion on this scheme can be found in the Imagineered new products section.

Wireless RFID Smart Key Detector:  Many cars now use a key with an imbedded RFID microchip.  The microchip is read when the key is inserted into the car’s ignition.  The keys containing a microchip often look the same as most other keys. People duplicating car keys will often not know of the microchip.  This circuit will light a LED if it detects a key containing a 125KHz RFID chip.

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