Stabilized Feedback Light-Valve

Feedback affords controlled and undistorted damping of light-valve resonance. All electromechanical devices can be regarded as feedback circuits if their motional impedance is interpreted as a feedback counter-emf. Auxiliary amplification of this counter-emf produces stabilized motional feedback. Depending on whether the amplifier counter-emf is proportional to amplitude, velocity, or acceleration, the feedback tends to flatten amplitude, velocity, or acceleration response characteristic. The light-valve is a mechanically resonant device operated on an amplitude basis but with a velocity counter-emf. Velocity feedback increases the effective damping of the light-valves; reactive components in the electrical driving impedance and in the feedback-gain tend to shift the resonance frequency. At 0.71 of critical damping the steady-state frequency characteristic is peakless and the valve follows transient impulses quickly with only 6 per cent overshooting. The maximum “bucking power” opposed to the valve motion by the feedback amplifier occurs at 0.58 of ribbon resonance and is 8 db less than the low-frequency power of the driving amplifier. — An amplifier is described that has been designed in accordance with the theory for application of stabilized feedback to commercial light-valves.

Print ISSN

0097-5834

Published

1942-03

Content type

Original Research

DOI

10.5594/J09917