A very high-frequency transistor-only linear tunable companding current-mode integrator

A low-distortion tunable transistor-only integrator suitable for applicatio ns in the frequency range approaching the f(T) of transistors is presented. The circuit is a modified version of the recently introduced companding cu rrent-mode integrator utilizing the non-linear base-emitter diffusion capac itance of the BJT. A first-order approximation of the circuit characteristi cs is explained, followed by a brief discussion on the departure from ideal characteristics due to transistor nonidealities. Experimental and simulate d results of practical integrators are given to verify the feasibility of t he proposed modified circuit.