• CMOS INVERTERS FORM 125KHZ OSCILLATOR
  This circuit is similar to schematic 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 INVERTER PARALLEL LC OSCILLATOR
  I have used this parallel resonant LC oscillator circuit countless times.  The oscillator frequency is determined by the inductor and capacitor values.  I have shown an adjustable inductor to make it easy to set the frequency to a specific value.  Once set the frequency is fairly stable over supply voltage variations and temperature changes.  The values shown are for 125KHz but the frequency can range from tens of kilohertz to tens of megahertz.   With a 74HCU04 type inverter, it will oscillate down to about 1.5 volts.  If the frequency is low, you can also use a 74C04 (CD4069) inverter.

• CMOS NAND GATE FORMS GATED 125KHZ OSCILLATOR
  This circuit is similar to schematic 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.

• CMOS SCHMITT TRIGGER IC MAKES VCO
  By changing the supply voltage fed to a classic 4584 Schmitt trigger type oscillator, the oscillator frequency can be changed over a range of 50:1.  A 74HCU04 inverter is used at the output of the 4584 to maintain a constant TTL logic level signal.

Dave's Circuits:  Astable Oscillator Circuits         Audio Oscillator Circuits         Crystal Oscillators              
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