Saturday, 22 July 2017

operational amplifier - Bipolar Op Amp w/ Near Zero Offset?


My understanding is that if source resistance is low, a bipolar op amp has 10dB less noise than a JFET. I prefer the JFET op amps because the input offset is so low that you can eliminate coupling capacitors and associated componentry.


So is there a bipolar op amp that has a low enough offset that stages can be DC coupled? Even when using a large pull down resistor on the + input a for high impedance input stage?


This would be for audio BTW.


UPDATE: The following circuit is identical to Figure 14.1 of Small Signal Audio Design by Douglas Self minus the output cap and missing output load resistor which are 47uF and 22K in the book.


Line Input Stage from D. Self book


The next circuit is the circuit that I'm planning to actually use and is largely a combination of 2-3 circuits from the aforementioned book. I believe this circuit shows the impedance environment surrounding the 200uF cap that might be eliminated if a suitable op amp were to be identified. Vertical lines that run off the bottom are to ground.


line input similar to figure in D. Self book




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