The Design Of Transistor Characteristic Tracer Based On Embedded System

As the important electronic component, transistor is not only the foundation of the whole electronic industry, but also profoundly affects the development of the industry. As measuring instrument, transistor characteristic tracer plays an important role in the process of the selection and use of transistors. Traditional transistor characteristic tracer mostly uses the pure hardware circuit, which is based on the analog electronic circuit, there is no digital interface, and it is bulky. With the application of the embedded system and the development of microelectronics technology, it provides transistor characteristic tracer with technical support of digitization, networking and intelligence development. In this thesis, the design method of transistor characteristic tracer based on the embedded processor has been studied, it can realize the automatic measurement, calculation and display of relevant parameters. It can be used as the basis of the experimental teaching of electronic information engineering in colleges and universities.The principle and unit circuit composition of the transistor characteristic tracer have been briefly introduced in this thesis as well as its structure characteristics. A digital transistor characteristic tracer has been designed, which is based on the embedded microcontroller STM32F103. The hardware architecture design of the tracer is presented in detail. The whole system consists of microcontroller unit module, signal generating circuit module, signal acquisition and control module and display module, which focus on the introduction of the principle and design of signal generating circuit and data acquisition circuit. The weak current signal of the collector (the voltage on both ends of precision sampling resistor) is sampled after amplified by instrumentation amplifier. The corresponding measurement control software has been designed, which is based on the Keil μVision integrated development environment. The base step current signal is produced by the controlled different digital potentiometer resistance through microcontroller unit SPI interface. The collector scanning voltage signal is generated through the output adjustable analog voltage of DAC. Built-in type 12-bit successive approximation ADC is used to sample the voltage of the base and collector. To improve the measurement precision, the average median filtering algorithm is adopted to calculate the results of each point multiple samplings, and displayed on LCD driven by FSMC bus. The display of input/output characteristic curve of transistor under test is realized by adopting point depiction method. The PC program is based on Lab VIEW graphical language, and control commands are sent to the microcontroller unit through network ports or receive sampling data and save it.Finally, the relevant hardware and software test data and the experimental results are put forward in the thesis, the results show that the designed transistor characteristic tracer can run normally. The resolution of ladder current source is 0.1uA, whose range is 0-160μA. And the resolution of scanning voltage source is 8mV, whose range is 0-30V. Compared with the laboratory existing tracer, the measurement error of the designed system is 0.24%, while its small volume, low cost and digital processing of the test results are remarkable advantages.