125Khz LC Oscillator - This circuit adds more invertors in parallel to deliver more power. It is similar to CMOS
INVERTERS FORM 125KHZ OSCILLATOR. Please note that the values shown are for 125KHz. . . . [Circuit by
Dave Johnson P.E., 03/12/02]
125KHZ Medium Power
Ocsillator - 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 . . . [Hobby Circuit designed by David Johnson P.E., 03/12/02]
125Khz Oscillator from
CMOS Inverters - This circuit 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 . . .
[Circuit by David Johnson P.E., 03/12/02]
125khz Oscillator with Medium Power - This
circuit adds even more inverters in parallel to deliver yet more power. The values shown are for 125KHz
. . . [Hobby Circuit designed by David A. Johnson P.E., 03/12/02]
Ultra Pure Sine Wave Signal Source - For some
RFID systems operating at 125KHz, a very low distortion signal source reference is needed. The circuit
shown on this page produces a 10-volt peak-to-peak signal into a 50-ohm load, with a distortion of only
0.01% . . . [Hobby Circuit designed by Dave Johnson P.E., 02/11/02]
12v Touch Switch Exciter
Circuit - This circuit is designed to
generate a 20KHz pseudo sine wave signal that can power about 50 remote touch activated switch circuits.
It can support a cable length of about 2500 feet. A typical remote switch circuit is also shown as well
as a receiver circuit for those switches. . . . [Circuit by Dave Johnson P.E., 02/10/02]
Controlled Oscillator (VCO) - If you need a
clean emitter coupled logic (ECL) type signal between 200MHz and 400MHz this circuit works fine. It uses
four voltage-controlled capacitors to change the frequency . . . [Circuit by Dave Johnson P.E.,
Battery Charger Using a 12v Solar Panel - A
while back I received an email from a guy in the UK. He wanted to use a small solar panel, designed to
charge 12v lead acid batteries, but use it to charge a 24v battery pack. His 24v battery pack used 20 AA
size NiMH cells. He went on to explain that his 20 cell NiMH battery pack was used very infrequently . .
. [Hobby Circuit designed by Dave Johnson P.E., 10/12/11]
300v Peak to Peak Signal
Generator - This circuit converts a square
wave signal to a +-150 volt output signal with fast 100nS rise and fall times . . . [Circuit by David A.
Johnson P.E., 06/03/00]
Generator-Fully Isolated - This circuit will
produce a single pulse at the zero voltage cross points of the power line voltage. An opto-coupler
provides a very safe 5KV isolation . . . [Circuit by Dave Johnson P.E., 12/12/04]
Generator is Line Powered - This circuit is
connected to the 120vac power line and transfers 60Hz clock pulses to a logic circuit. The optoisolator
used provides 5000 volts of isolation between the power line and the logic side of the circuit . . .
[Hobby Circuit designed by David A. Johnson P.E., 02/23/99]