PNP transistor used with Positive Power supply to Emitter and +ve biased.
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In this kind of configuration the transistor is biased by Positive voltage. Do to the characteristic of the PNP transistor reaction to a Positive supply at the emitter, the collector voltage will retain above the 600mv minimum switching voltage. Even when the vb (base bias voltage) reaches near 0vdc, the lowest the collector voltage will get is 650mv. Such configuration of a transistor is good where a circuit is expected to operate at high frequency and need not idle below the switching voltage. It also provides none inverting output. The transistor output is dependant of vb value, which can be trimmed by the resistor R3.
Such circuit is often used in video and like high frequency buffer circuit. It can also be used as sensory circuit or low-level amplifier.
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