Build the Colpitts oscillator shown using either breadboard (proto board) or strip board, then test the oscillator’s operation using a multi meter and oscilloscope. The Colpitts Oscillator is a particularly good circuit for producing fairly low distortion sine wave signals in the RF range, 30kHz to 30MHz. Colpitts oscillator working, circuit diagram and theory. Colpitts oscillator frequency equation. Colpitts oscillator using transistor and opamp.

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As the CE configured transistor provides o phase shift, it makes o phase shift between the input and output voltages. Draw the waveform on the grid. Instead of bipolar junction transistorsother active components such as field-effect transistors or vacuum tubescapable of producing gain at the desired frequency, could be used.

The Colpitts Oscillator Explained

A Colpitts oscillator is the electrical dual of a Hartley oscillatorwhere the feedback signal is taken from an “inductive” voltage divider consisting of two coils in series or a tapped coil. You may also like: Design an amplifier if you want an oscillator!

Hence it provides d. During this process, the electrostatic energy stored in the capacitor gets converted into magnetic flux which in turn is stored within the inductor in the form of electromagnetic energy. Cin is the input DC decoupling capacitor while Cout is the output decoupling capacitor.

Other components in the circuit are the same as that found in the case of common-emitter CE colpirt is biased using a voltage divider network i.

Module 2.4

On acquiring the maximum charge feasible, they start to colpittt via the inductor L. An oscillator is used to produce electronic signal with oscillating periods. Other components such as the tank circuit elements, coupling capacitors etc have no significant effect in the gain of an opamp based Colpitts oscillator. Capacitors C1, C2 and inductor L1 forms the tank circuit.


The effective capacitance and the inductance form a bandpass filter that is very colpktt at the frequency of interest, allowing the amplifier to build up oscillations at that frequency. These terms can be included later in a more rigorous analysis.

It is much similar to the Hartley oscillator except the addition of tank circuit. Oscillatot, feedback is properly phased to produce continuous Undamped oscillations. But remember that a larger output voltage will also mean a higher collector current.

Having built the Colpitts oscillator, either on breadboard or strip board, check that the circuit is oscillating satisfactorily, then complete the measurements in Tables 1 and 2. Notify me of new posts via email. This type of oscillator is widely used in inductive loop vehicle detectors. As a result the equation for frequency can be simplified as. The capacitors C c and C b are employed to block d.

The only difference is colpittt there is one additional capacitor connected in series to the inductor in the tank circuit.

Due to the excellent performance in the high frequency region, the Colpitts oscillator can be even used in microwave applications. The Pierce oscillator, with two capacitors and one inductor, is equivalent to the Colpitts oscillator.

Simple common-base Colpitts oscillator with simplified biasing.

The capacitor C e provides a. Its action, known mathematically as a harmonic oscillator, is similar to a pendulum swinging back and forth, or water sloshing back and forth in a tank.

All types of electronic oscillators use their input voltage to control the oscillation frequency. Colpitts[1] is one of a number of designs for LC oscillatorselectronic oscillators that use a combination of inductors L and capacitors C to produce an oscillation at a certain frequency. A Colpitts oscillator looks just like the Hartley oscillator but the inductors and capacitors are replaced with each other in the tank circuit.

The resistors R 1R 2 and R e provide necessary bias condition for the circuit. Temporarily stop the oscillations by connecting a 0. Connects Facebook Youtube Videos. This 68 ohm resistor could be replaced by a slightly higher or lower value to alter the amplifier gain for experimentation.


Thanks for all the details. The actual frequency of oscillation will be slightly lower due to junction capacitances and resistive loading of the transistor. Sine wave, square wave etc. Further, this signal is provided with an additional phase-shift of o by the transistor which results in a net phase-shift of o around the loop, satisfying the phase-shift criterion of Barkhausen principle.

The Colpitts oscillator is a time-tested design — from Colpitts oscillator using opamp. Please I need a colpitts oscillator for 1ghz frequency with dbm power output using opamp, pls help me. RF Sine Wave Oscillators 3.

colitt This is also an important circuit when a crystal is part of the feedback circuit instead of an inductor. Given all other values, the input resistance is roughly. This method will be used here to determine conditions of oscillation and the frequency of oscillation. As the name implies, linear oscillators are used to produce linear or sinusiodal waveforms. Leave a Reply Cancel reply Your email address will not be published.

This results in better frequency stability as well as a better sinusoidal output waveform. It is unusual to show an op-amp oscillator, and it is interesting to think about the design changes and limitations discussed in the video. Your email address will not be published.

You can tell a Colpitts oscillator by the two capacitors in the feedback circuit.

Colpitts Oscillator Circuit diagram & working. Frequency equation. Colpitts oscillator using opamp

Periodic oscillation starts for a critical bias current and colptit the variation of the bias current to a higher value chaotic oscillations are observed. For this reason the circuit is also called a tank circuit. Email required Address never made public.