Editing Colpitts oscillator (section)

===Practical example===
[[File:Colpitts Osz JFET Gate.gif|frame|Figure 3: Practical common-gate Colpitts oscillator with an oscillation frequency of ~10&nbsp;MHz]]

Fig.&nbsp;3 shows an example with component values.<ref>{{cite book   
  | last = Hayward
  | first = Wes
  | title = Introduction to Radio Frequency Design
  | chapter = Figure 7.12 Colpitts oscillators using a JFET
  | publisher = ARRL
  | year = 2004
  | location = US
  | page = 281
  | url = https://archive.org/details/isbn_9780872594920
  | doi = 
  | id = 
  | isbn = 0-87259-492-0}}</ref> Instead of [[field-effect transistors]], other active components such as [[bipolar junction transistor]]s or [[vacuum tube]]s, capable of producing gain at the desired frequency, could be used.

The [[common-gate|common gate amplifier]] has a low input impedance and a high output impedance. Therefore the amplifier input, the source, is connected to the low impedance tap of the LC circuit L1, C1, C2, C3 and the amplifier output, the drain, is connected to the high impedance top of the LC circuit. The resistor R1 sets the [[operating point]] to 0.5mA drain current with no oscillating. The output is at the low impedance tap and can drive some load. Still, this circuit has low [[Distortion#Harmonic_distortion|harmonic distortion]]. An additional [[variable capacitor]] between drain of J1 and ground allows to change the frequency of the circuit. The load resistor RL is part of the simulation, not part of the circuit.