Hi, I'm designing an electrect microphone pramplifier that is supplied by 5V. I decided to use OPA1612 because of it's low noise input levels. I heared that I should be aware about Input current noise density - provide low impedance at input and use proper feedback resistors. Here is the circuit I have designed:
Should I remove R3 to lower input impedance and maybe use second chanel for second stage, so I could lower feedback resistors? I was planning to use second channel as 1/2 Vcc voltage buffer. The line_out should provide consumer line level (max 0.89 Vpp). As you can see I used j-fet in common drain mode for low output impedance.
Should I remove R3 to lower input impedance and maybe use second chanel for second stage, so I could lower feedback resistors? I was planning to use second channel as 1/2 Vcc voltage buffer. The line_out should provide consumer line level (max 0.89 Vpp). As you can see I used j-fet in common drain mode for low output impedance.