Robinson oscillator
Encyclopedia
The Robinson oscillator is an electronic circuit originally devised for use in the field of continuous wave (CW) Nuclear Magnetic Resonance
Nuclear magnetic resonance
Nuclear magnetic resonance is a physical phenomenon in which magnetic nuclei in a magnetic field absorb and re-emit electromagnetic radiation...

 (NMR). It was a development of the Marginal oscillator. Strictly one should distinguish between the marginal oscillator and the Robinson oscillator, although sometimes they are conflated and referred to as a Robinson marginal oscillator. Modern Magnetic Resonance Imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...

 (MRI) systems are based on pulsed (or Fourier Transform) NMR; they do not rely on the use of such oscillators.

The key feature of a Robinson Oscillator is a limiter in the feedback loop. This means that a square wave current, of accurately-fixed amplitude, is fed back to the tank circuit. The tank selects the fundamental of the square wave, which is amplified and fed back. This results in an oscillation with well-defined amplitude; the voltage across the tank circuit is proportional to its Q-factor.

The marginal oscillator has no limiter. It is arranged for the working point of one of the amplifier elements to operate at a nonlinear part of its characteristic and this determines the amplitude of oscillation. This is not as stable as the Robinson arrangement.

The Robinson oscillator was invented by the ingenious British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

 Neville Robinson
Neville Robinson
Frank Neville Hosband Robinson was an Englishphysicist....

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