English: Negative resistance oscillator circuit used with current controlled negative differential resistance (CCNR) devices. CCNRs require high impedance DC bias, and are stable for load impedances greater than their differential resistance r, so they are called open-circuit stable devices. Therefore they are often used in circuits like this, with a current source I_bias (which could be a voltage source in series with a resistor) to bias the device, and a series resonant circuit LC as a load. The series resonant circuit has a low impedance at its resonant frequency but a high impedance at all other frequencies, so the circuit will be unstable and oscillate only at the resonant frequency.