The datasheet for the SAP16 temperature compensated darlington transistors recommends a bias current of 2.5mA down the diode biasing chain. In a practical power amp, this current would also flow through the VAS stage. But 2.5mA is quite low for the VAS, and I would normally use 2 or 3 times that.
Has anyone tried the SAP devices at higher bias chain currents, and if so, does the temperature compensation still work OK ?
Chris.
Has anyone tried the SAP devices at higher bias chain currents, and if so, does the temperature compensation still work OK ?
Chris.
the bias chain of diodes is ~ 5diodes + a variable resistor.
What voltage do you expect across this combination? Maybe 2.5V?
what parallel resistor would be required to pass the excess current through the VAS? Maybe 470r.
Leave a couple of extra pads to add one or two parallel resistors to trim the diode current once you get it running.
What voltage do you expect across this combination? Maybe 2.5V?
what parallel resistor would be required to pass the excess current through the VAS? Maybe 470r.
Leave a couple of extra pads to add one or two parallel resistors to trim the diode current once you get it running.
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