A parametric amplifier (paramp) is an extremely low- noise amplifier for ultra-high frequencies, microwaves and light signals. The parametric amplifier operates as an active inductor or capacitor whose reactances are periodically changed by a different frequency.
In the microwave parametric amplifiers, the reactance of the parametric amplifier is formed by a varistor and its parametric values are changed by a pump oscillator whose frequency is not the same as the input frequency. The variable reactance belongs to an oscillating circuit tuned to the input frequency.
The amplification of the input signal is achieved by the periodic change of the reactance. Energy is supplied to the system via the pump oscillator and the reactance is constantly changed. This change acts like a negative resistor, resulting in the amplification of the input signal. Parametric amplifiers are very low noise because the reactance has no thermal noise. They can also produce a fairly high output power.
Unlike laser amplifiers, parametric amplifiers are designed for wider frequency ranges. In optical parametric amplifiers, the gain bandwidth is determined by the dispersive characteristics and the length of the amplifier crystal. The amplification occurs exclusively during the pumping process.