| 摘要 |
An auto-biasing virtual circuit mechanism for a bipolar transistor is independent of the biasing and the configuration of a signal waveform application circuit in which the transistor is installed. The virtual circuit comprises a plurality of AC signal coupling elements (capacitors) coupled in circuit between respective ones of a plurality of AC signal access terminals and respective ones of the base, collector and emitter electrodes of the transistor. Because of their frequency dependent impedance characteristics, each coupling capacitor effectively provides a short circuit coupling path for AC signals, while blocking or being an open circuit for DC bias inputs. Conversely, DC biasing is effected through large valued inductors, which provide short circuit coupling paths for DC bias inputs, while blocking or being open circuits for AC signal conditions. A controllable DC voltage bias source, which is coupled through an inductor to the emitter electrode of the transistor generates an output voltage corresponding to the difference between the collector voltage (Vc) and the required collector-emitter bias voltage (Vce) of the transistor, so that the effective differential voltage applied across the collector and emitter electrodes of the transistor is the desired value of Vce. The output terminal of a controllable collector current (Ic) current source is coupled directly to the collector electrode of the transistor.
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