Think of a simple Colpitts Oscillator Circuit like a child on a swing; the inductor and capacitors act like the swing system, and they make the signal move back and forth continuously.
But swing can slow down also; for that transistor come for help, it is like friend push a kid and keep swing move nice and steady.
Hence, same way Colpitts oscillator keep wave go ON and ON not stop.
Circuit Working:
Parts List:
| Components | Values | Quantity |
|---|---|---|
| Resistors | 10k 1/4 watt | 2 |
| 2.2k 1/4 watt | 1 | |
| Capacitors | Ceramic 100nF | 1 |
| Ceramic 100pF | 2 | |
| Semiconductors | Transistor 2N2222 | 1 |
| Coil inductor 0.2mH | 1 |
In this post we can learn how LC oscillator work and also to build one type of Colpitts oscillator; oscillators are very important in electronics so we see them in clocks, radios and computers.
Furthermore, they make wave signals and different types are RC, LC and crystal where each one is good for different work.
There is no best oscillator but which one to use depend on our circuit.
Here, capacitor and inductor L and C make wave and capacitor charges and give energy to inductor and inductor give it back in opposite way and this go on and on by making oscillation.
But wave die slowly because of resistance; but to keep wave going we use amplifier and feedback and this feedback give lost energy back and this make steady sine wave.
Colpitts oscillator can make signal like 30 MHz.
For LC oscillator with transistor two things important feedback must be in same phase and strong enough to cover energy loss.
Q is quality factor and it show how good the circuit keep wave and big Q mean better; also quartz crystal has very high Q which is much better than LC circuit.
Formulas:
Colpitts Oscillator Frequency Formula:
This formula tell how to find Colpitts oscillator frequency (f):
f = 1 / (2 * π * √(L * Ceq))
where:
- f is frequency in hertz Hz.
- L is inductor value in henry H.
- Ceq is capacitor equivalent value in farad F.
How to Find Ceq Equivalent Capacitance:
In the circuit, capacitors C2 and C3 connect in series, so we calculate the equivalent capacitance (Ceq) as follows:
1/Ceq = 1/C2 + 1/C3
Important Note:
This formula give simple idea of oscillator frequency.
But in actual circuit exact frequency can change because of many things like small error in components, extra small capacitance from wires and behavior of transistor.
How to Build:
To build a Simple Colpitts Oscillator Circuit we need to follow the below mentioned steps:
Connect the Components:
- First, assemble all the components according to the circuit diagram, be careful with capacitor polarity and the placement of the inductor if it is not symmetrical on both sides.
Bias the Transistor:
- Use resistor R1 to give bias to transistor as this make sure transistor work in active mode not cutoff or saturation.
Apply Power:
- Connect power supply with positive wire connects to Vcc and negative wire to ground.
Adjustment:
- If required we need to change capacitor and inductor values to get correct frequency, so try different values and tune it little bit.
- After we connect all the parts, turn ON the power and use an oscilloscope or frequency counter to check the output signal..
- If result is not good then change values and test again until it works well.
Note:
- Making oscillator need some knowledge of electronics so be sure we understand how it work before trying and be safe when working with circuits and power.
Conclusion:
Overall, Simple Colpitts oscillator circuit is basic LC circuit as it make stable sine wave signal.
Also, it use capacitors and inductor for feedback and one amplifier to keep oscillation going; so by changing parts in feedback for capacitors and inductor, we can set the frequency we want.