Transistors In Common Emitter Configuration Research Articles

Analysis and design of a SiGe-HBT based terahertz detector for imaging arrays applications

In this paper, we will introduce a new designed direct conversion terahertz detector. Characteristics of this new detector have been compared with a prefabricated design in order to obtain better performance of our new proposed design. We have introduced an exponentially graded base SiGe-HBT instead of linearly graded ones, and have used a single transistor with two base contacts, which is equivalent to two transistors in common emitter configuration. New proposed detector has been analyzed by both compact circuit and two dimensional carrier transport models. Responsivity and minimum noise equivalent power of new detector are about 4.9 A/W and 6.5 pW/Hz1/2 at 700 GHz respectively, while these characteristics for the prefabricated detector, are about 1 A/W and 50 pW/Hz1/2. Also about 231μW/pixel decrement in power consumption for the same responsivity, and a same bandwidth have been achieved.

Medium-power GaAs bipolar transistors

GaAs has an advantage over Si and Ge in some material parameters for bipolar transistor application. Another benefit is the availability of the wide gap emitter principle for GaAIAs/GaAs heterojunction transistors. Such bipolar transistors have been fabricated and tested. Maximum frequency of oscillation fMAG = 2.2 GHz and cut-off frequency fT = 2.7 GHz demonstrate the high-frequency suitability, whereas emitter-collector breakdown voltages VCEO100 V and maximum collector currents IC max ∼ 300 mA are an indicator of high-power applications. The transistor operates at temperatures in the range of − 269°C to + 350°C. A double heterostructure NpN transistor shows the elimination of the turn-on voltage of ∼ 0.2 V for Npn wide gap emitter Ga0.7Al0.3As/GaAs transistors in common emitter configuration. The NpN transistor can be operated in bi-direction with comparable current gain due to the wide gap emitter principle and the symmetry of the emitter-base and collector-base heterojunctions. Compared with the Npn GaAs transistor, the storage time ts of the NpN GaAs transistor is reduced by a factor of about 2.

On the fall time of silicon planar transistors with constant base current drive

In the active region transient response of a transistor in common emitter configuration with constant base current drive, there is some discrepancy in theoretically predicted and experimentally observed fall time. It has been explained by taking into account an additional turn-off base current drive which is usually ignored due to the emitter-base voltage of the transistor in the fall time expression using charge-control model of the transistor. The calculated values of the fall time of various silicon planar transistors are verified experimentally.

Stability of high-frequency transistor in common-emitter configuration

This letter describes the stability of the common-emitter transistor in terms of the y parameters in the high-frequency range; the graphical representation of the normalised input admittance of the transistor is also shown. This representation is useful and convenient for investigating performance of the input admittance in both design and analysis of circuits. The maximum frequency of potential instability of the common-emitter transistor is established using an approximate high-frequency equivalent circuit of a junction transistor.