RF OSCILLATOR CIRCUITS


Posted on Feb 6, 2014

A popular circuit known as a Hartley oscillator. Its identifiable feature is the tapped coil in the LC tank circuit. Notice that the coil`s tap point is grounded. The amplifier portion of the oscillator is a common-emitter amplifier. Therefore, the ac base voltage and ac collector voltage are 180 out of phase. This means that the feedback network must provide an additional 180 phase


RF OSCILLATOR CIRCUITS
Click here to download the full size of the above Circuit.

shift so that the feedback voltage is of the correct phase to sustain oscillations. To help you understand the circuit`s operation, it has been redrawn in Fig. 2-2( b). Notice that L 1 is in parallel with L 2 and C 3 in series. At the resonant frequency of the tank circuit, the net reactance of the L 2 C 3 branch appears capacitive. Also, the net capacitive reactance of the L 2 C 3 branch equals the inductive reactance of the L 1 branch. This gives us the following mathematical relationship.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Overvoltage Protection for the LM317
Safe-constant-current-source
simple switch off time delay schematic
How to design 65nm FPGA DDR2 memory
Intro to Intan Amplifier Chips
Mini DDS circuit
Two-Stage JFET Preamp/Booster
A typical circuit for the LM4910 two-channel amplifier



Top