Pulse-Frequency Modulation

272

03:01:50

This 555-based PFM modulator has good sensitivity (<= 100 mV) and excellent linearity. The 1 kHz modulating signal is applied to the base the pnp transistor which works as a controlled current source. The PFM signal at inverter's output is passed through an LPF with cutoff frequency about 1 kHz, which performs demodulation. The LED does not do any special function here and is just a replacement for a low-voltage Zener diode.

published 10 years ago

hurz

10 years ago

Good linearity, yes. But bad temperature behavior ;-) hfe will change of current source BJT

stanislav_maslovski

10 years ago

Sure :) I wanted to make it minimalistic Let me change the polarization circuit :)

stanislav_maslovski

10 years ago

Is it better now? ;)

hurz

10 years ago

Much better :-)

add comment in editor

EveryCircuit is an easy to use, highly interactive circuit simulator and schematic capture tool. Real-time circuit simulation, interactivity, and dynamic visualization make it a must have application for professionals and academia. EveryCircuit user community has collaboratively created the largest searchable library of circuit designs. EveryCircuit app runs online in popular browsers and on mobile phones and tablets, enabling you to capture design ideas and learn electronics on the go.