what do you think of matching the single pair of transistors? does it really required to match the 5200 1943? i mean n and p for one pair?
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The fundamental differences between any N&P transistor pairs means Hfe matching is not really what you think.
As long as Hfe is in the same grouping of R,O,Y etc. it will be sufficient for HiFi.
As long as Hfe is in the same grouping of R,O,Y etc. it will be sufficient for HiFi.
A big difference between the Vbe of the N from the Vbe of the P will be adjusted out by the DC offset adjustment.
A big difference between the hFE of the N from the hFE of the P results in a net addition to or net subtraction from the current being sourced or sunk from the VAS.
This could result in a weird VAS performance if the VAS current is way off from the target operating current.
A big difference between the hFE of the N from the hFE of the P results in a net addition to or net subtraction from the current being sourced or sunk from the VAS.
This could result in a weird VAS performance if the VAS current is way off from the target operating current.
True, but normal practice is to design the VAS with enough current for the lowest hFE transistor you might buy, plus some safety factor, say 30% or 50% extra.
So in each case, the driven transistor "takes what it needs".
Asymmetry is not damaging, as far as it's within design parameters.
*If* an abnormally poor hFE transistor got past the quality control, well, it's a QC control problem, not a design one.
So in each case, the driven transistor "takes what it needs".
Asymmetry is not damaging, as far as it's within design parameters.
*If* an abnormally poor hFE transistor got past the quality control, well, it's a QC control problem, not a design one.
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