Composition diagram of transformer feedback LC oscillator circuit

Regarding the composition of the transformer feedback LC oscillation circuit, the circuit includes the basic components of the sinusoidal wave oscillation circuit, such as the amplifier circuit, feedback network and frequency selection network. The LC parallel circuit acts as the collector load of the BJT and plays a frequency selection role.

Transformer Feedback LC Oscillation Circuit

1. Circuit composition

Figure 1 is a transformer feedback LC oscillation circuit.

The circuit includes the basic components of a sine wave oscillation circuit, such as an amplifier circuit, a feedback network and a frequency selection network. The LC parallel circuit acts as the collector load of the BJT and plays a frequency selection role.

Feedback is realized by the secondary winding N2 of the transformer. The instantaneous polarity method is first used to analyze the phase condition of the oscillation circuit.

2. Phase balance condition judgment

Reference for judging phase balance conditions.

Figure 1 Transformer feedback LC oscillation circuit

3. Oscillation and amplitude stabilization

The amplitude condition for the transformer feedback LC sine wave oscillation circuit to start oscillation is that the loop gain is greater than 1. As long as the transformer ratio and BJT are properly selected, the amplitude condition can generally be met.

The stabilization of the oscillation is achieved by utilizing the nonlinearity of the amplifier device.

When the amplitude is large enough, although the current waveform of the BJT collector may be obviously distorted, since the collector load is an LC parallel resonant circuit with good frequency selection effect, the output voltage waveform is generally not distorted.