An Improved Synchronous Detector
Walter C. Michels, Esther D. Redding · Review of Scientific Instruments · 1949
The synchronous amplifier design of Michels and Curtis has been modified to minimize feedback and so to allow preamplification and high sensitivity. The resulting instrument has a voltage sensitivity of 2×105 mm/volt with an inductive input impedance of 2×106 ohms. The frequency selectivity is sufficiently sharp so that the band width is of the order of 0.25 c.p.s. at 800 c.p.s. Advantages and disadvantages of the synchronous detector are discussed.