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Amber 3501 Current-boosted Output Stage

Posted: Thu Jun 01, 2023 1:40 pm
by mediatechnology
Some time ago I explored the ADI and Burr-Brown current and voltage-boosted outputs and noticed the similarity of it to the Amber 3501 output stage.

I posted about the AD and Burr-Brown circuit here: viewtopic.php?p=6664#p6664
Op Amp Booster Stage +/-36V Analog Devices AN-106

INA105 with voltage-boosted output to provide almost rail-to-rail performance TI Application Note SBOA009

This circuit fragment shows how current feedback is returned from the boosted output into the INA105's output stage emitter.
"Q3" is the top output transistor internal to the INA105.
Note how this is virtually identical to the +/-36V output stage shown earlier.

INA105 shown with current feedback returned to the output stage emitters. TI Application Note SBOA009
While looking at the Amber schematics I noticed that they were able to cleverly embellish the ADI and Burr-Brown circuits to provide a low-distortion output.

Amber 3501 Current-Boosted 5534 Output Stage Using Current Mirrors

I may build one of these someday just to see how it performs. When I do I'll move the bias trimmer which really should be in the base-emitter circuit to gracefully accommodate trimmer failure.