Complex signal generators based on capacitors and on piezoelectric loads

We briefly analyze and demonstrate several nonlinear signal generators, according to the principles proposed in [1]. These systems apparently should not oscillate, because they include only capacitors in the positive feedback loops. However, the design attempted to make use of the well-known parasitic elements of the capacitors to create a selective feedback loop with physical capacitors only. The use of the resonant (piezoelectric) load adds a new potential mode of oscillation. The design aimed to make achievable as many as possible frequency points where oscillation modes ay exist, against the rather common belief that a single oscillation mode can be supported at one time in electronic oscillators. For this purpose, variable, independent gains have been provided to the positive feedback loops that correspond to the various modes in the circuit. We describe the schemes, briefly analyze their behavior, show simulation and experimental results, and discuss potential uses. The paper is largely based on [1].