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A new perspective on current-sharing hybrid amplifiers
A new perspective on current-sharing hybrid amplifiers
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Old 24th November 2020, 07:00 PM   #11
stocktrader200 is offline stocktrader200  Canada
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Lm1875 is not unity gain stable
Av greater then 10 to be stable.
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Old 24th November 2020, 08:55 PM   #12
kokoriantz is online now kokoriantz  Lebanon
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The circuit is stable on simulator. The feedback is not only unity voltage also current. If stability is a problem,22k feedback resistor and 2.2k shunt resistor makes the amp stable with unity gain.
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Old 25th November 2020, 02:23 AM   #13
indra1 is online now indra1  Indonesia
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I think inputs of LM1875 are not designed for large signal swing.
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Old 25th November 2020, 04:02 AM   #14
kokoriantz is online now kokoriantz  Lebanon
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Hi Indra. What makes you think as such. The datasheet doesn't speak anything particular about it. The circuit diagram shows diodes on each input constraining the inputs to the rails as well a limiting diode between the inputs.

I have a personal question. I stayed in Bogor about a month in 2001 studying about tropical trees in the botanical garden. Near the entrance was a market place, where on the walkway, along with vegetable vendors, was a young man about 16/17 years old assembling power amplifiers 3055/2955 base from a to z and selling them like pancakes. Every morning as I greeted him, made me feel so tiny. Do you know him?
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Old 25th November 2020, 06:29 AM   #15
indra1 is online now indra1  Indonesia
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Hi, with max supply at +- 30V and stability at gain >10, there was little need for the inputs to handle > 3V swing. Of course the real limit needs to be tested, but no surprise if distortion starts to jump at a relatively low voltage swing at the inputs. Perhaps it is more rewarding to bootstrap an op amp driving a follower, then add the current multiplier and other desired enhancements.

Sorry, I do not know the young man you mentioned, from late 90s to about a couple years ago I was mostly in Jakarta.
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Old 25th November 2020, 09:06 AM   #16
kokoriantz is online now kokoriantz  Lebanon
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Indeed most opamps distort when reach rail voltages to see if the dropout 4v is sufficient to maintain the input transistors biased . The Michaels purpose is to reflect the output and plate impedances to each other so that the speaker sees the nonlinear character of the plate and the plate sees the reactive and resistive elements of the speaker. By this you can use a small triode and make it resemble to a high power SET, ingenious idea, Thank you Michael.
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Old 25th November 2020, 09:10 AM   #17
kokoriantz is online now kokoriantz  Lebanon
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Quote:
Originally Posted by stocktrader200 View Post
Lm1875 is not unity gain stable
Av greater then 10 to be stable.
More discussion about stability is taking place here How to parallel multiple power amps?
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