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#1
Posted to rec.audio.tech
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Opamp Neg Feedback question
Looking at the negative feedback loop in a lot of opamp gain stages (even
unity gain), there is often a capacitor from a few pF to around 100 pF in parallel with the feedback resistor. What's the idea behind this? I'm guessing it effectively forms some kind of low-pass filter, as the higher frequencies passed by the cap will be attenuated. Is this supposed to stabilize the circuit from some kind of HF oscillation? I'm particularly looking at the output stages of various mic preamp circuits. Some don't have this capacitor in the negative feedback loop and some do. Any pearls of wisdom out there? Bill. |
#2
Posted to rec.audio.tech
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Opamp Neg Feedback question
"Bill Ruys" wrote
in message Looking at the negative feedback loop in a lot of opamp gain stages (even unity gain), there is often a capacitor from a few pF to around 100 pF in parallel with the feedback resistor. What's the idea behind this? Puts in a high frequency roll-off. I'm guessing it effectively forms some kind of low-pass filter, as the higher frequencies passed by the cap will be attenuated. Right. Is this supposed to stabilize the circuit from some kind of HF oscillation? Reduces HF noise from the input. I'm particularly looking at the output stages of various mic preamp circuits. Some don't have this capacitor in the negative feedback loop and some do. Any pearls of wisdom out there? Most well-designed audio gear has a pole in the 50 KHz - 100 KHz range. Grants some immunity to EMI, etc. |
#3
Posted to rec.audio.tech
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Opamp Neg Feedback question
Arny Krueger wrote: Most well-designed audio gear has a pole in the 50 KHz - 100 KHz range. Grants some immunity to EMI, etc. Glad to see the audio industry in keeping our former eastern block Polish people employed. See ya on the s plane......... Bob ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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