With Temperature Protection Circuit, Sige Power Transistor Designs

With the development of semiconductor technology, SiGe HBT is widely used in the field of high frequency for its advantage of excellent character about frequency and power, material, technology, price and so on.However, as the integration of IC is higher and higher and the size of device is smaller and smaller, which makes the transistors often work on high current density. Meanwhile because of the application of modern SOI technique and low thermal resistanc in device isolation techniques, the influence of self-heating and thermal conpling effect aroused by power dissipation of devices and circuits are more remarkable and make their performances degenerate. So for a long time the main problem of SiGe HBT is the current concentration and over temperature phenomena.Firstly, this thesis elaborates the structure, technology, application of power SiGe HBT and the relationship between the temperature characteristics and electrical characteristics, summarizes the reasons of over temperature in the working of high power SiGe HBT. Secondly, the thesis discusses different methods of over temperature protection to the SiGe HBT. In the end based on the compatibility of SiGe and conventional Si technology, especially the compatibility with CMOS process this thesis designs a kind of over temperature protection circuit which is used for power chips. This solution avoids the output resistor's influence on the gain of power and large number of mathematical calculations.For the over temperature protection circuit, it designs the functional models such as temperature sensor, comparator using hysteresis, current mirrors and the controller. By simulating the resolution, frequency response, propagation delay time and work of whole circuit, it proves that this circuit achieve the requirements of the design. Test results show that this method can protect power SiGe HBTs effectively. In addition, it gets rid of the deterioration of the output power, power gain, power additive efficiency (PAE) and saturation voltage usually caused by ballasts resistors.So, this solution of over temperature is simple and practical.