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dawsonjon / PicoRX

Build a SDR SW/MW/LW Receiver with a Raspberry Pi Pico
MIT License
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NE5532P opamp issue #92

Closed mryndzionek closed 1 month ago

mryndzionek commented 1 month ago

I've tested NE5532P opamp. It's 10MHz bandwidth and noise density of 5 (at 1kHz), but it doesn't seem to be working. Recommended minimum supply voltage is 5V. I'm powering from USB, which after diode drop is 4.6V. Could this be the issue? Some sources claim that it operates from 3V.

dawsonjon commented 1 month ago

I haven't tried it myself, but it's quite a popular option for this type of thing. You could try a 5v power supply to eliminate the voltage drop as a possibility? Maybe power on Vbus rather than Vsys? What are the symptoms? Is the op-amp saturating or sitting around mid supply rail?

mryndzionek commented 1 month ago

I haven't tried it myself, but it's quite a popular option for this type of thing. You could try a 5v power supply to eliminate the voltage drop as a possibility? Maybe power on Vbus rather than Vsys? What are the symptoms? Is the op-amp saturating or sitting around mid supply rail?

The receiver shows extremely low signal, barely breaking S0 squelch on some frequencies. I also tried LM358P and it works! Just a little bit more noise than MCP6022. I think this is faulty chip. I'll have some more in few days, so I'll check then.