dielectric amplifier[‚dī·ə′lek·trik ′am·plə‚fī·ər]
an amplifier of electric oscillations in which the amplification is created by a change in the capacitance of a capacitor containing a ferroelectric when the voltage supplied to it changes. In a typical amplifier stage of a dielectric amplifier (see Figure 1), the electrical oscillations being supplied change the capacitance, and thus the reactance, of the capacitor C, causing modulation of the oscillations generated by the generator G. The modulated oscillations produced at the terminals of the load resistor Zt are detected by the diode D. As a result of the detection of the oscillations at the output terminals of a field amplifier, oscillations arise that have the same shape as the oscillations at the input terminals but greater amplitude. The capacitors containing a ferroelectric are frequently connected to the amplifier stage of a dielectric amplifier with a bridge circuit.
The power gain for a single dielectric amplifier stage can be as high as 100 for low-frequency oscillations (hundreds of hertz to a few kilohertz). For higher frequencies (up to a few megahertz), the gain factor falls off significantly (to 10 or less). To produce higher gain in dielectric amplifiers, as in tube and transistor amplifiers, several stages may be connected in series.
The operating principle of dielectric amplifiers is similar to that of magnetic amplifiers; both kinds of amplifiers are used mainly in the amplification of low-frequency oscillations, in automated equipment, and in signaling equipment.