Posted on May 5, 2012

Two comparators and a summing amplifier that generate differential harmonic spectra comprise a simple frequency multiplier. The resulting circuit can extract harmonics from a sine, triangle, sawtooth, or any other sloping-sided waveform. With a sloped-input waveform, a comparator produces an output pulse width that`s proportional to the input amplitude plus a reference voltage. Changing the reference can vary the pulse width from 0 to lOO%. As the pulse width changes, the harmonic spectrum changes, but two comparators combined in the adder eliminate harmonics, depending on the duty cycle.

Click here to download the full size of the above Circuit.

For example, a 50% pulse will lack all the even-numbered harmonics. Similarly, a 25% duty-cycle pulse will be missing multiples of the fourth harmonic and deliver the second, sixth, and tenth harmonics. Accordingly, the circuit generates multiples of the input frequency that might not have existed in the input waveform. Adjusting the references can create virtually any harmonic. Because comparators Al and A2 supply differential inputs to the added A3, the adder cancels out equal harmonics. Therefore, both Al and A2 should have identical ac characteristics, and A3 should have good common-mode rejection and a high slew rate. In particular, Rl, R2, and R3 should match within 0.1%. Of course, the accuracy of the circuit depends heavily on the amplitude stability of the input.

Leave Comment

characters left:

New Circuits



Popular Circuits

The ATL-3 Loop Antenna
Tube Amplifier Isolates High Voltages
art364 / Standalone Arduino
Muscular Bio stimulator
led workbench lighting
light activated police siren using 555 timer
speedometer project
TDA1562Q Audio Amplifier Circuit
VHF FM Antenna Booster Circuit
Infrared-Led based Wireless Data & Voice Communication withCircuit
Solid State Tesla Coil/High Voltage Generator Circuit
Novel White LED Torch
Portable Battery Charger Using Renewable Energy Sources like Solar or Wind Project