If I put my notes here, I might be able to find them again later!
Voltage Regulators for Line Level Audio. Part II : The Pass Transistor
Part 2 of a series.
Instead of pulling the output current through R1, we add an npn pass transistor, Q1. The output current now "passes" through the transistor, while the Zener diode still regulates the output voltage by being connected to the transistor base.
The output impedance falls to a few ohms, but the ripple rejection improves only slightly.
This is a useful basic circuit block for audio, but the ripple rejection can easily improved by the addition of a couple of additional components, as we'll see shortly.
Instead of pulling the output current through R1, we add an npn pass transistor, Q1. The output current now "passes" through the transistor, while the Zener diode still regulates the output voltage by being connected to the transistor base.
The output impedance falls to a few ohms, but the ripple rejection improves only slightly.
This is a useful basic circuit block for audio, but the ripple rejection can easily improved by the addition of a couple of additional components, as we'll see shortly.
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