1. In the electrical interface design, the reflection attenuation is usually deteriorated in high frequency conditions because the transmission line reflection with loss is related to frequency. In this case, the PCB trace is shortened. It is very important.
2, the regulator diode is a diode of a stable circuit operating voltage. Due to the special internal structure characteristics, the inverse breakdown is applied, as long as the current is limited, this breakdown is non-destructive.
3, PN knot has a good mathematical model: switch model → diode is born → then come back to a pn knot, the triode is born.
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5, under high-density occasion, because the transceiver signal is smashed, it is easy to crosstalk, this should comply with the 3W principle when wiring, that is, the centerline spacing of adjacent PCB traces is 3 times higher than the PCB line width. In the plug equipment, the position of the connector is connected, there are many grounding needles to provide a good RF circuit.
6, bipolar tube is current control device, controlling a larger collector current through a small current of the base, and the MOS tube is a voltage control device, and the source canopy is controlled by the gate voltage.
7. The triode is working by the movement of the carrier. Taking the NPN tube pole follower as an example. When the base is added to the voltage, the PN junction composed of the base region and the transmit zone is to prevent the polym (the base region is Diffusion motion of the hole, the transmitting area is electronically, in which an electrostatic field (ie, the built-in electric field) is induced by the transmitting area (i.e., the built-in electric field) in this PN junction.
8, Schottky Diode (SCDTKY, SBD) is suitable for high frequency switching circuits, positive voltage drop and inverting pressure, low (0.2V), but the reverse breakdown voltage is low, and the leakage current is also large.
9. Most of the jitter characteristics depends on the characteristics of the output chip, but if the PCB wiring is not properly, the power filter is not sufficient, the clock reference source is too large, and the jitter component will also increase. The matching of the signal line has a direct impact on jitter. In particular, the chip contains a multiplier function, which is a large phase noise.
10, polar choice means that BJT is also used in PNP or NPN, which should be considered while determining the power form. Some triodes are connected to a certain electrode, and for silicon tubes is often a collector. This factor should be considered when needed for a certain ground.
11. Field effect transistors and BJT have a big difference in the work process: The charge carrier in BJT is a hole or a small amount of "small child", the charge in the FET is the number of free numbers of freedom. Electronics, "Mono".
12, the emitter is polarized, the collector is reflected as the prerequisite for the BJT working in an enlarged working state. Three connection modes: common base, common emitter (maximum, because of current, voltage, power can be enlarged), co-collector electrode. A method of discriminating three configurations: the co-emitter input, the collector output; the co-collector input, the emitter output; the common base, the electrode input, the collector output.
13, the main parameters of the triode: current amplification coefficient β, pole reverse current, (collector maximum allowable current, the maximum intensive power of the collector, the reverse breakdown voltage = 3 important limit parameters determine BJT working in the security area) .
14. Because the RGS of J-FET is very high, you should first pay attention to no static operation when in use, otherwise the gate breakdown is easily happened; it should be carefully considering each limit parameter when designing the circuit, and cannot be exceeded. When the J-FET is used to make a variable resistor, it should ensure that the device has the correct bias and cannot enter the constant current area.
15. Amode bias circuit: It is used to eliminate the effects of temperature on static operating points (Double power is better).
16. Comparison of three BJT amplification circuits: all-scale amplifying circuits, current, voltage can be enlarged. Circular electrode amplifying circuit: only amplify current, follow the voltage, input R large, output R small, used as input stage, output stage. Common base amplifying circuit: only amplify voltage, follow current, high frequency characteristics.
17, decoupling capacitor: output signal capacitance ground, filter off the high frequency clutter of the signal. Bypass Capacitor: Input signal capacitance ground, filter off the high frequency clutter of the signal. The AC signal is processed for these two capacitors as a short circuit.
18. MOS-FET In addition to correctly selecting parameters and correct calculations, the most emphasized is still an anti-static operation problem, during circuit debugging, welding, and installation, must operate in strict accordance with the anti-static program.
19. The mainstream is an IC from the emitter to the collector, and the bias flow is from the IB of the emitter to the base. Relative to the main circuit, the circuit for providing a current is a so-called bias circuit.
20, three aluminum electrodes of field effect: gate G, source S, drain D. The base B, an emitter E, a collector C of the triode are respectively corresponding, respectively. < The source needs to be launched, so the English name of the emitter E, the gate of the gate is Gate, the same existence, and the base of the base. 1882. The P-type substrate is generally connected to the gate G.
21. The enhanced FET must rely on the gate source voltage VGS to function (turn on the voltage Vt), the depletion FET does not require a gate source voltage, under the positive VDS action, there is a large drain current flow to the source ( If the negligible VGS, the clamp may occur, at this time, the voltage is a clamp voltage VP *** Important feature ***: Can work under the positive and negative gate supply voltage)
22. The MOS tube of the N-channel requires positive VDS (equivalent to the VCC of the triode to the collector) and a positive VT (equivalent to the VBE of the triode base and the emitter of the emitter), while the MOS tube of the P-channel requires a negative VDS And negative VT.
23, VMOSFET has high input impedance, low drive current, fast switching speed, high frequency characteristics; negative current temperature coefficient, no heat malignant cycle, thermal stabilization is excellent.
24. When an operational amplifier is applied, a negative feedback current is generally applied.
25. Differential amplification circuit: Difference mode signal: the difference between the two input signals. Total mode signal: The sum of the two input signals is 2. Thus: Differential mode and common mode definition indicates that the two input signals obtain an important mathematical model: any input signal = common mode signal ± differential mode signal / 2.
26. The differential amplifying circuit only places a large differential mode signal to suppress common mode signals. Using this characteristic, it can suppress the effects of external factors such as temperature on circuit performance. Specific performance indicators: common mode suppression ratio kcmr.
27. When the diode is switched from the positive deflection to the anti-bias, there will be a larger reverse recovery current from the cathode to the anode, and the reverse current rises first to the peak, and then falls to zero.
28. In the ideal case, if the two transistors current of the push-pull circuit, the voltage wave is completely symmetrical, and the output current will have no even harmonic component, and the push-pull circuit is known from the active harmonic. In fact, due to the total difference in the two tube characteristics, the circuit is also impossible to symmetrically, so the output current will also have the doll harmonic component, in order to reduce nonlinear distortion, because of the presence of the tube as much as possible.
29. In order to obtain large output power, the voltage is added to the power transistor, the current is very large, and the transistor is operated in a large signal state. Such a safety work of transistors is an important issue of power amplifiers, generally not limited to the limit parameters (ICM, BVCEO, PCM) exceeding the tube.
30. Interference of the amplification circuit: 1, remotely away from the amplifying circuit 2, input stage shield 3, DC supply voltage fluctuation (using a voltage regulator power supply, input, and output plus filter capacitance).
31. Four configurations of negative feedback amplifying circuit: voltage series negative feedback (stable output voltage), voltage parallel and negative feedback, current string negative feedback (stable output current), current parallel and negative feedback.
32, voltage, current feedback determining method: output short path method, set RL = 0, if the feedback signal does not exist, it is voltage feedback, and that is, it is current feedback.
33. Decision method of series, parallel feedback: The feedback signal is summed by the input signal. If it is in the form of a voltage, it is a series feedback. If it is in the form of a current, it is in parallel feedback.
34. For NPN circuitry, for the common configuration, it can be roughly understood to control VE (VBE = VB-VE) by control VB, and further control IC (from The potential flows into the C pole, you can also see the C pole as a funnel of the inlet water.
35. For digital circuitry, VCC is the power supply voltage of the circuit. VDD is the working voltage of the chip (usually VCC>vdd), and VSS is a grounding point; in the field effect tube (or COMS device), VDD is a drain, VSS is the source, VDD, and VSS referring to component pins, and does not represent power supply voltage.
36. The oscilloscope probe has a ground line and a signal line. The ground is the one of the oscilloscope input terminals. It is generally a clip-shaped, and the signal line generally has a probe hook, and if you connect the oscilloscope ground. Your device, connect the signal line terminal to your signal, note that if the signal to be measured and the mains are not isolated, it cannot be directly measured.
37. There are two cases of driving ability: First, the device's input resistance is too small, the output waveform is deformed, such as the TTL level driver does not relate the relay; the second is that the device inputs the resistor enough, but does not reach the power of the device, such as small Power amplifier, drive high-power speakers, speakers, but the volume is small, in fact, the voltage is not large enough.
38. Filtering circuit: With the energy storage effect of the reactance element, it can play a good filtering. Inductance (series, high power) and capacitance (parallel, small power) can function as a wavelet.
39. Switch regulator power supply and linear power supply: linear power supply, low efficiency, strong heat, but output is stable. Switching power supply, high efficiency, typical fever, but output ripples, need to be smooth.
40. The type of fault caused by the electrical circuit is: the performance of the electronic component such as transistor, capacitance, resistance, changes in the performance of the performance of the electrical components; the failure of the line contacts in the electronic circuit. The types of electronic circuits caused by the external causes are: technicians do not operate according to the instructions when using electronic circuits; maintenance technician maintenance procedures are not standardized.
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