Hi,
I am building a frequency detection to detect the following frequencies: 20kHz, 40kHz, 60kHz, and 80kHz.
I am using phototransistors to detect the light sources and have a transimpedance followed by a coupling circuit and a gain stage which then feeds into my bandpass filter which covers all four frequencies.
My circuit works but when i add a bit more gain to get a further distance (of about 6-8 feet) i start getting a lot of noise problems. I am just curious as how to get rid of my noise problems. The noise is causing the output waveform to change the frequency. And i have tried sheilding my phototransistors which electrical tape.
If anyone has any info. on how to get rid of the noise that would be greatful. By the way, I am using an LM837 op amp for my transimpedance stage. I have access to the LM837, LM741, and TL081 op amps.
I am building a frequency detection to detect the following frequencies: 20kHz, 40kHz, 60kHz, and 80kHz.
I am using phototransistors to detect the light sources and have a transimpedance followed by a coupling circuit and a gain stage which then feeds into my bandpass filter which covers all four frequencies.
My circuit works but when i add a bit more gain to get a further distance (of about 6-8 feet) i start getting a lot of noise problems. I am just curious as how to get rid of my noise problems. The noise is causing the output waveform to change the frequency. And i have tried sheilding my phototransistors which electrical tape.
If anyone has any info. on how to get rid of the noise that would be greatful. By the way, I am using an LM837 op amp for my transimpedance stage. I have access to the LM837, LM741, and TL081 op amps.