A new minimum component current feedback operational amplifier based sinusoidal oscillator

Author(s): Li Ya, Qi Ya-ping

A new current-feedback operational amplifier (CFOA) based sinusoidal oscillator circuit is presented and tested. The circuit uses only one externally connected inductor and exploits to advantage the internal poles of the CFOA. A complete analysis of this circuit with respect to its dynamic properties is given. The AD844 can be used in place of traditional op amps, but its current feedback architecture results in much better ac performance, high linearity, and an exceptionally clean pulse response. Experiments show that sinusoidal oscillation at frequency of 122.1 MHz was obtained using the AD844 CFOA and an inductor of inductance = 0.14uH with peak-to-peak output voltage=700 mV. This is the highest frequency of oscillation obtained using the AD844 CFOA. The offset voltage and input bias currents of the circuit are laser trimmed to minimize dc errors; VOS drift is typically 1 μV/°C and bias current drift is typically 9 nA/°C.  Peak output rate of change can be over 2000 V/μs for a full 20 V output step. Settling time is typically 100 ns to 0.1%, and essentially independent of gain

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