Injection-lock a Wien-bridge oscillator

摘要

I recently had the opportunity to investigate a new micropower 6-MHz LTC6255 op amp driving a 12-bit, 250k sample/sec LTC2361 ADC. I wanted to acquire the FFT of a pure sinusoid of about 5 kHz. The problem is that getting the FFT of a pure sinusoid requires, well, a pure sinusoid. Most programmable signal generators, however, have fairly poor noise and distortion performance, not to mention digital "hash" floors, compared with dedicated op amps and good ADCs. You can't measure 90-dB distortion and noise using sources that are "60 dB-ish."