Onkyo A-SV610PRO, Service Manual

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PNP Transistor behavior with Negative supply and bias.
[[Rectangular box shows DVM]]
Positive as ground reference; Q1 is biased by the supply voltage -ve, variable depending on the value of
R3. In such configuration Q1 can be turned off completely. The output of Q1 collector is equal to the vb
less the 600mv loss within the transistor. Output should be expected to invert. Such configuration may be
used as Voltage dependant switching and control such as amplifier bias stage, ALC, and sensory circuits.
The ability to vary the output of Q1 collector form zero to its maximum given supply voltage less the
component switching loss, makes the circuit widely usable in the audio, video and general power supply
manufacturing industry. The configuration is normal for PNP transistor with a negative voltage supply at its
Emitter.