Grid-leak detector
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A grid-leak detector is a combination diode rectifier and audio amplifier. In the circuit, the grid of a triode vacuum tube corresponds to the plate of a diode, rectifying action thus occurs. A d.c. current is permitted to flow through the grid leak, via a resistor that biases the grid negatively, and the frequency variations in voltage across this resistor are amplified through the tube as in a normal audio amplifier. In the plate circuit an r.f. choke is installed to eliminate the r.f. in the output circuit.
A grid-leak detector has considerably greater sensitivity than a diode. The sensitivity is further increased by using a tetrode or pentode instead of a triode. The operation is equivalent to that of the triode circuit except controlled feedback is applied and controlled by adjustment of the screen-grid voltage.
Although the regenerative grid-leak detector was one of the more sensitive detectors of its day, its many disadvantages limited it for use only in the simplest receivers.
