A common base amplifier (29) has an input (31) and an output (32). A transistor (33) has an emitter coupled to the input (31) of the amplifier (29), a collector coupled to the output (32) of the amplifier (29), and a base coupled to a voltage reference (34) provides low input impedance and unity current gain. A control circuit (38) controls a first bias circuit (36) and a second bias circuit (37). The second bias circuit (37) is coupled to the collector of the transistor (33) and provides a bias current for the transistor (33) while transistor (33) outputs the bias current which is received by the first bias circuit (36). Control circuit (38) determines the current magnitude for both the first bias circuit (36) and the second bias circuit (37) and ensures that the current magnitudes are maintained at a fixed ratio.
A process combines a high performance silicon pin diode (60) and other semiconductor devices such as transistors, resistors, and capacitors. The pin diode (60) is formed beneath an epitaxial layer (44) of the device at a depth that maximizes absorption of light having a wavelength greater than approximately 600 nanometers. Devices such as transistors are formed in the epitaxial layer (44). An integrated circuit has a substrate (41), an intrinsically doped layer (42), a buried layer (43), and an epitaxial layer (44). An isolation region (45) isolates an intrinsically doped region (46), a buried layer region (47), and the epitaxial layer region (48). The pin diode (32) has a substrate (41), an intrinsically doped region (46), and a buried layer region (47). A polysilicon region (62) provides a top side contact for the pin diode (60).
An apparatus comprising a common-base amplifier circuit and a control circuit. The amplifier circuit may be configured to generate an output signal having a transimpedance bandwidth in response to an input signal. The control circuit may be (i) coupled between the output signal and the input signal and (ii) configured to provide a DC offset adjustment by providing current steering at the input signal.
An augmented common-base transistor amplifier circuit is described, including an input terminal and an output terminal. The amplifier circuit also includes an augmentation circuit, connected from the emitter to the base of the amplifying transistor, which detects an error voltage at the transistor emitter, amplifies and inverts the error voltage, and then applies the amplified error voltage to the base of the amplifying transistor, for the purpose of reducing the emitter error voltage and thus linearizing the common-base amplifier. According to a further embodiment, a second transistor is used for amplifying the emitter error voltage, and a further embodiment uses a transformer for augmentation. Circuits are described for single-ended, push-pull, and complementary amplifiers.
Among the embodiments of the present invention is an apparatus that includes a transistor, a servo device, and a current source. The servo device is operable to provide a common base mode of operation of the transistor by maintaining an approximately constant voltage level at the transistor base. The current source is operable to provide a bias current to the transistor. A first device provides an input signal to an electrical node positioned between the emitter of the transistor and the current source. A second device receives an output signal from the collector of the transistor.
Among the embodiments of the present invention is an apparatus that includes a transistor (30), a servo device (40), and a current source (50). The servo device (40) is operable to provide a common base mode of operation of the transistor (30) by maintaining an approximately constant voltage level at the transistor base (32b). The current source (150) is operable to provide a bias current to the transistor (30). A first device (24) provides an input signal to an electrical node (70) positioned between the emitter (32e) of the transistor (30) and the current source (50). A second device (26) receives an output signal from the collector (32c) of the transistor (30).
