Robinson oscillator
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 Robinson oscillator is an electronic oscillator circuit originally devised for use in continuous wave (CW) nuclear magnetic resonance (NMR). It was invented by the British physicist Neville Robinson in the 1950s.
Continuous-wave NMR is usually detected by measuring the change in quality factor of an electrical resonator containing the sample to be measured. In early NMR experiments, this was done by driving the resonator with an oscillating current and measuring the amplitude of the resulting voltage. However, a disadvantage of this method is that any difference between the frequency of the oscillator and of the resonator leads to a voltage that is indistinguishable from the signal due to NMR.
In Robinson's circuit, the electrical resonator is incorporated into the oscillator. This ensures that the oscillator frequency always coincides with the resonator frequency, making the NMR signal clearer. While such an arrangement had been used previously (the so-called marginal oscillator)., Robinson's innovation was to insert a limiter into the feedback loop of the oscillator; this has several benefits including more precise control of the oscillating magnetic field applied to the sample.