The Robinson oscillator is an electronic oscillator circuit originally devised for use in the field of continuous wave (CW) nuclear magnetic resonance (NMR).[1] It was invented by the Oxford-based British physicist Neville Robinson in the 1950s.[2]
 Transistor circuit for a Robinson oscillator | |
| Component type | Electronic oscillator |
|---|---|
| Working principle | Oscillator with a limiter in the feedback loop |
| Inventor | Neville Robinson |
| Invention year | 1959 |
The oscillator was a development of the marginal oscillator.[3] Strictly, one should distinguish between the marginal oscillator and the Robinson oscillator should be distinguished, although sometimes they are conflated and referred to as a Robinson marginal oscillator. Modern magnetic resonance imaging (MRI) systems are based on pulsed (or Fourier transform) NMR; they do not rely on the use of such oscillators. 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 key feature of a Robinson oscillator is a limiter in the feedback loop.[4] 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.[5]
Improvements to the circuitry for the Robinson oscillator have been made using integrated circuits[6] and MOSFET transistors.[7]
See also
editReferences
edit- ^ "Robinson oscillator". ChemEurope.com. Retrieved 23 August 2025.
- ^ Robinson, F. N. H. (1959). "Nuclear Resonance Absorption Circuit". Journal of Scientific Instruments. 36 (12): 481–487. Bibcode:1959JScI...36..481R. doi:10.1088/0950-7671/36/12/301.
- ^ Newton, Michael I.; Breeds, Edward A.; Morris, Robert H. (October 2017). "Advances in Electronics Prompt a Fresh Look at Continuous Wave (CW) Nuclear Magnetic Resonance (NMR)". Electronics. 6 (89): 89. doi:10.3390/electronics6040089.
- ^ "6. Robinson Oscillator". Electron Spin Resonance. Retrieved 23 August 2025.
- ^ "Robinson Oscillator". Electron Spin Resonance – HW Part. PhysicalOpenLab. 2 March 2021. Retrieved 23 August 2025.
- ^ Deschamps, P.; Vaissiére, J.; Sullivan, N. S. (June 1977). "Integrated circuit Robinson oscillator for NMR detection". Review of Scientific Instruments. 48 (6): 664–668. Bibcode:1977RScI...48..664D. doi:10.1063/1.1135103.
- ^ Wilson, K. J.; Vallabhan, C. P. G. (May 1990). "An improved MOSFET-based Robinson oscillator for NMR detection". Measurement Science and Technology. 1 (5): 458–460. doi:10.1088/0957-0233/1/5/015.
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