A Lock-In Amplifier for Fluorescent Light Detection

An integrated on-chip lock-in amplifier has been developed for fluorescent light detection for biological applications. The system includes 2.1 mm x 2.1 mm tiny chip using a photodiode transimpedance amplifier topology for the pre-amp, followed by gain amplifier, demodulator and filtering stages. Synchronous demodulator or phase sensitive detector stage has two different architectures to demonstrate the difference between the results. The recommended transmitting light frequency is between 0.5 kHz to 5 kHz. We used 1 kHz frequency for the test.