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An electro-thermal feedback model for multi-finger power SiGe heterojunction bipolar transistor (HBT) was presented in this paper. Based on the model, the influence of the change of emitter finger spacing on the surface temperature distribution of SiGe HBT was investigated. It is found that under the same bias conditions, with the increase of emitter finger spacing, the peak junction temperature drops...
Based on the electro-thermal feedback model for multi-finger power SiGe heterojunction bipolar transistor (SiGe HBT), this article analyzes the effect of base heavy doping on thermal characteristic of SiGe HBT. Because of the effect of base heavy doping, SiGe HBT will produce bandgap narrowing which decreases the collector current density and affects the device thermal distribution. By analyzing the...
A novel SiGe HBT low noise amplifier (LNA) was designed by adopting the feedback resistors, which are low cost and implemented easily in VLSI technology. Due to the absence of on-chip spiral inductor, the die area of this novel LNA decreases noticeably. The novel resistive feedback structure of the LNA comprising a shunt feedback loop and a series feedback loop, wherein the shunt feedback loop is...
In this paper, the IC-VBE characteristic of bipolar transistors are described by novel analytical formulations, which for the first time present the expression of collect current in the second fly-back point. Through the analytical formulations, it is found that a smaller emitter ballast resistance can make the collector current achieve the second fly-back point before transistors are burned-out,...
A novel multi-finger power SiGe heterojunction bipolar transistor (HBT) with non-uniform finger length and non-uniform finger spacing was proposed to improve the thermal stability. Thermal simulation for a ten-finger power SiGe HBT with novel structure was conducted with ANSYS software. Three-dimensional temperature distribution on emitter fingers was obtained. Compared with traditional structure...
A novel multi-finger power SiGe heterojunction bipolar transistor (HBT) with segmented emitter fingers and nonuniform segment spacing was proposed to improve the thermal stability. Thermal simulation for a ten-finger power SiGe HBT with novel structure was conducted with ANSYS software. Three-dimensional temperature distribution on emitter fingers was obtained. Compared with traditional emitter structure,...
We report a novel PIN diode SiGe HBT variable gain amplifier (VGA) suited for the standard of WCDMA. The PIN diode which is employed in the feedback loop of the VGA play as a variable resistor to realize the gain control function. By adjusting the bias of the diode, the gain of the VGA can be changed. An inductor is utilized in the feedback loop to reduce the noise figure of the circuit. After matching...
With a three-dimensional thermal-electrical model, a non-uniform emitter length structure in multi-finger SiGe heterojunction bipolar transistors (HBTs) is presented to improve thermal stability. Compared with the traditional uniform emitter length design, the peak temperature of multi-finger SiGe HBT with non-uniform length is lowered. Therefore, it can operate at large current and has a higher power...
A high dynamic range linear-in-dB variable gain amplifier (VGA) using SiGe HBT devices for WCDMA applications is presented in this paper. The gain is achieved through four stages of amplifiers. The first, third and the fourth stage is the normal amplify stage, and the second stage is the gain control stage. The gain control is implemented by adjusting the bias of the second amplifier. The VGA is driven...
A design methodology of Darlington low noise figure (LNA) for application at ultra wide bandwidth using a resistive feedback scheme is proposed. The packaged SiGe heterojunction bipolar transistors (HBTs) BFP740 and chip type passive components were used for this direct-coupled LNA. The Darlington amplifier has high gain of 20 dB with variation of 0.5 dB over 3.1-6 GHz, which is twice of single stage...
Based on a three-dimensional thermal-electrical model, non-uniform finger spacing power SiGe HBT was designed and fabricated. Experiment result shows that the peak temperature of non-uniform spacing SiGe HBT is Iowed by 22 K compared with that of uniform space HBT. For the same nonuniform spacing HBT, temperature non-uniformity among the fingers is improved obviously at different biases. The higher...
For power bipolar transistors, the emitter-ballasting-resistor is usually used to improve the thermal stability. However, the ballasting-resistor degrades the output power, power gain, power-added efficiency (PAE) of the transistor. In this paper, the thermal stability can be improved substantially by adjusting either the spacing or length of the emitter fingers without using ballasting resistors...
Taking into account of the temperature dependence of emitter junction voltage, the valence-band discontinuity at emitter junction (DeltaEv), and the bandgap narrowing due to heavy doping (DeltaEg), a simple method to optimize the ballasting resistor of RF power heterojunction bipolar transistor (HBT) has been presented based on the thermal-electric feedback network analysis. The agreement between...
For power bipolar transistors, the emitter-ballasting-resistor is usually used to improve the thermal stability. However, the ballasting-resistors degrade the output power, power gain, power-added-efficiency (PAE) of the transistor. In this paper, the thermal stability can be improved substantially by adjusting either the spacing or length of the emitter fingers without using ballasting resistors...
Base on the thermal-electric feedback network analysis, the thermal stability factor S is presented to express the thermal stability of the device. It is shown that the self-heating effect is compensated completely and the electrical characteristic of device won't shift when S=0. Furthermore, the expression of the minimum ballasting resistance R c of HBT to compensate the self-heating effect is presented...
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