Here it is shown how to first build and simulate a Colpitts oscillator in multisim and then build and test the oscillator on a breadboard. This allows one to check whether the multisim simulated circuit works as expected in reality and how much deviation there is from simulation and actual implementation. Also it is shown here how to determine the Colpitts oscillator feedback network capacitors and inductor values, how to determine the biasing resistors values, how to determine the coupling capacitors values and the bypass capacitor values. These values can be directly determined using online Colpitts oscillator calculator and BJT amplifier design calculator.
The following is the circuit diagram of the Colpitts oscillator that was build in multisim.
The amplifier of the oscillator is made up of the 2N3904 transistor and biasing resistors R1, R2, R4. The values of the biasing resistors can be directly calculated using the BJT Amplifier Design Online Calculator. The C5 capacitor is the emitter resistor bypass capacitor and capacitors C3 and C4 are the coupling capacitors. The value of these bypass capacitor and coupling capacitors for the Colpitts oscillator can also be found out from the BJT amplifier design calculator. The calculatedl values from the calculator is shown below.
After the Colpitts oscillator circuit is build it is simulated and the output checked using the Tektronix TDS2024 4 channel 200MHz oscilloscope.
The oscillator output signal on the oscilloscope is shown below.
The Tektronix TDS2024 oscilloscope was used to measure the Colpitts oscillator frequency which was around 42.2MHz as shown below.
The following video shows simulation of the Colpitts oscillator in Multisim and measurement of the output signal using the Tektronix 2024B oscilloscope.
Next the above Colpitts oscillator circuit was build on a breadboard which is shown below.
The oscilloscope output was measured using the UNI-T UTD2102CEX 100MHz oscilloscope which is shown below.
The measured signal frequency was around 47MHz. There was fluctuation of the signal and of the frequency giving measurement in the range 40MHz to 49MHz. This is shown in the following video.
