Grid-leak detector
（重定向自Grid leak）
A grid-leak detector is a thermionic valve (UK, Australia, NZ etc.), or vacuum tube (USA), circuit used in older vacuum tube AM radio receivers, which served as a combination amplifier and detector (rectifier) to extract the audio signal from the modulated radio frequency signal. The tube used a grid leak circuit to generate the DC grid bias voltage necessary for proper operation from grid current that occurs in all vacuum tubes due to electrons attracted to the grid during the positive part of the RF cycle.