"Lehmann" Buffer Output Transistors. - diyAudio
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Old Yesterday, 05:08 PM   #1
ammel68 is offline ammel68  United States
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Default "Lehmann" Buffer Output Transistors.

I have a question about the BD139 & BD140 output devices in the Lehmann buffer circuit below.

The schematic calls for the BD139 & BD140-16 devices which have the highest hFE.

What happens if you substitute the lower hFE devices like the BD139 & BD140-6 or -10?

Thank you...
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File Type: png BD140_hFE.png (75.2 KB, 62 views)
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Old Today, 06:39 AM   #2
Mooly is offline Mooly  United Kingdom
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I would imagine that you would see a slight increase in distortion at higher output levels when driving lower impedance loads.
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Old Today, 04:22 PM   #3
ammel68 is offline ammel68  United States
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I was concerned of saturating or "overloading" the output transistors since the BC transistors are also the highest hFE "C" grade devices.
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