Design and production of transistor icon, Transistor Characteristic Exhibit Instrument
Keywords: transistor icon circuit diagram
Author: Du Zhihao Wang Hong Xue Yun Ren
Transistors illustrate instruments for measuring transistors input, output characteristic curves. In the experiment, teaching and engineering by using the icon, the actual characteristics of the transistor can be obtained, and the function of the transistor can be better. This simple transistor icon is simple, the price is low, easy to use, can meet the case where numerical accuracy is not high. Used in conjunction with the normal oscilloscope, the input, output characteristic curve of the NP tube can be measured. In addition, this design also expands the transistor polarization, transistor magnification measurement, display, and speech broadcast function. First, the system principle The picture below is the system block diagram. The output characteristic of the transistor refers to the relationship between the voltage UCE between the transistor collector and the emitter between the transistor current electrode and the emitter. The relationship between the electrode current Ic. Each LB corresponds to a output characteristic curve. The plurality of LB corresponding to the plurality of LBs are simultaneously displayed on the oscilloscope, and a cluster output characteristic curve can be obtained. The input characteristic of the transistor refers to the relationship between the voltage UHE between the transistor base and the emitter between the transistor base and the emitter in a certain UCE. Each UCE corresponds to an input characteristic curve. When a plurality of UCEs corresponding to the plurality of UCEs are simultaneously displayed on the oscilloscope, a cluster input characteristic curve can be obtained. Therefore, a simple transistor icon is mainly composed of the following three parts, namely: base current generating circuit, collector scan voltage generating circuit, and magnification measurement display circuit, as shown below. When the output characteristics of the transistor are displayed, the base step current generating circuit is directly generated by the single-chip control DAC2; the collector scan voltage generating circuit is generated by the single-chip control DAC1 generates an increased voltage from zero, and then via the voltage amplification circuit. Enlarge with the desired scan voltage. When the input characteristics of the transistor are displayed, the DAC2 is directly produced by the microcontroller; the sketch is controlled by the microcomputer, and the DAC2 generates the desired step voltage and the serrated wave signal to enlarge the voltage amplification circuit to generate the desired scan. Voltage. The above two mode conversion is completed by the button on the MCU single-chip microcomputer in the Lingyang SPCE061A. The magnification measurement display circuit consists of single chip, digital tube and meter amplifying circuit. The single chip receives the processing sampling voltage, and the average number of samples is sampled, and the magnification is obtained, and then the single-chip BCD decodes is sent to the external digital tube display. In circuit implementation, this design also considers a number of factors such as accuracy, streamline and low cost, and has made many innovations and improvements.
Second, hardware design Lingyang SPCE061A single-chip function is strong, good compatibility, high cost performance, high volume, high integration, high degree of reliability, small power consumption, and comparable data processing and computing power, the highest system The clock frequency can reach 49MHz and is running fast. Since the A / D, D / A converter is integrated inside the single-chip microcomputer, there is no need to add A / D, D / A devices. By sampling sample, the internal A / D, D / A is combined, and the closed-loop feedback adjustment control is constituted, and the R hardware circuit is simplified, and the measurement accuracy is improved, and the measurement error can be used to compensate for measurement errors. This gives debugging, maintenance and function expansion. Increased performance, it has brought great convenience. With the powerful voice broadcast function of Lingyang SPCE061A microcontroller, as long as the simple Lingyang self-contained audio compressed file and library file, the transistor is magnified. 1. Instrumentation amplifiers For improved accuracy, the acquisition circuit uses three operations to form an instrumentation amplifier. As shown below. The current collector resistance and the base resistor upper voltage are obtained by the circuit, and the voltage is proportional to the current, so current signal is obtained. The instrument amplifier has high precision, low power consumption, high mode suppression ratio, working frequency bandwidth and input impedance, and can accurately measure IC and IB. The UCE and IC are then transmitted to the oscilloscope to obtain the output characteristic curve. UBE, LB is transmitted to the oscilloscope to obtain a losing characteristic curve.
2. Polarization circuit transistor type discriminator circuit utilizes an in-phase comparator. As shown below. Since the current flow of the NPN type and PNP transistors is reversed, according to theory and repeated measurement, when the two transistors are structurally structured in the figure, the connection mode is the same (i.e., the electrode is connected to the upper end, the emitter is attached to the lower end), if the transistor is NPN When the type, the emitter voltage is about 1V, while the PNP type is about 6V at least 6V. According to this, the appropriate threshold voltage is set, and the inverting input is connected. When the transistor is an NPN type, the emitter voltage is always less than the threshold voltage, so the light emitting diode is not bright; when the transistor is a PNP type, the emitter voltage exceeds the threshold voltage, the output high level, the light-emitting diode, that is, the transistor type can be discriminated.
3. Display circuit pair display circuit, this design abandon complex plurality of digital pipe decoder 7448 driving the traditional circuit displayed by the digital tube, using software programming to complete the decoding process, directly drive the digital tube display. 4. Plate and Welding For better implementation of this design, when designing printed circuit boards, pay attention to applying copiers should be as short as possible and avoid parallel to each other to reduce parasitic capacitance. The corner of the copper wire should be rounded or bevel. The spacing between the width of the copper wire and the adjacent copper wire is preferably less than 0.3 mm. The public ground wire of the copper wire should be placed as much as possible on the edge portion of the board. The copper foil should be kept as much as possible on the board, which can enhance the shielding capacity. The analog circuit is grounded with a digital circuit to eliminate interference. In addition, the PCB of the digital circuit can be used to form a loop or mesh - that is, a ground wire is used to use, and the ground wire of the analog circuit cannot be arranged. After the printed circuit board is completed, according to the size of the small to large welding element, order: resistance, capacitance, diode, triode, other components, etc. The Safety Welding Sentence Sequence of Integrated Circuits is: Ground → Output → Power End → Input. Welding time is as short as possible in the premise of ensuring welding, and each solder joint is preferably 3s to avoid damaging the device. I am free to sell the iron impurities to avoid excessive flux. After the soldering is completed, there is a need to check that there is no leakage and domain welding. When checking, you can use the tweezers to lightly mention each component, see if it is shaken.
Third, the software design general engineering program includes initialization procedures, DAC synchronous outputs all the way tooth waves and all walks of stepped waves, I / O timing sampling AD conversion procedures and voice broadcast programs. Among them, by pressing the button selection output characteristic mode (DAC2 generating step current, DAC1 generating a zigzag voltage) and the input characteristic mode (DAC2 generates a serrated current, DAC1 generates a step voltage). The total flow chart is shown below.
After testing, this icon operates stable, reliable, and the acquisition data is more accurate, and the transistor polarity can be correctly judged and has a voice broadcast, which has achieved satisfactory results. The magnification test data is shown in the table below. The output characteristic curve is shown below. The following table is magnified in multiple test data (using DT9806 four half-digital multimeter)
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