Push-pull oscillator
A push-pull oscillator is an electronic circuit for generating vibrations. It uses at least two electronic switches (mostly transistors ) that alternately conduct electricity. Since the circuit is very robust, it is mainly used as an inverter in motor vehicles at low frequencies . The predecessors were the error-prone mechanical chopper . In the high-frequency range , a push-pull oscillator has the advantage that the temperature-dependent transistor capacitances are connected in series and parallel to the resonant circuit have less influence on the frequency generated. Before special procedures for frequency stabilization - such as PLL technology - were used, push-pull oscillators were therefore also popular in radio technology for generating VHF and UHF signals.
RF application
The push-pull oscillator generates a sinusoidal oscillation with few even harmonics . As with the push-pull amplifier , the two identical quadratic characteristics of the FETs add up to a linear overall characteristic. The circuit can deliver significantly more power than other oscillator circuits.
functionality
The resonant circuit consists of the winding L2 of the transformer and the capacitor C1. Due to the positive feedback "crosswise" as with the multivibrator , either FET Q1 or FET Q2 is conductive. If the voltage at the drain of Q1 falls because Q1 is better controlled, the gate voltage at Q2 also falls and the drain voltage at Q2 rises. The gate voltage of Q1 also increases and Q1 is controlled even better. The transition between conducting and blocking of the individual FET is not abrupt in the push-pull oscillator as in the multivibrator, but has the shape of a half sine wave . The adjacent circuit oscillates at approx. 7 MHz .
literature
- ↑ Jogi's tube booth, basics of amplifier construction, push-pull operation with tubes
- ↑ Heinrich Schröder, Electrical Communication Technology, Volume II, Verlag für Radio-Foto-Kinotechnik, chap. B.III.9.a, p. 229.