To ensure the safety and security of the user of green laser pointer

green laser pointer includes the presentation, museum, inspection and so on
In this condition the temperature dependence of APD's internal gain is particularly evident in a small temperature changes can cause great changes in the gain. Theory can be proved that the gain of the APD is a function of the bias and temperature, the two together determine the gain size of the APD operates. Temperature drift of the APD bias compensation principle: Let the APD bias voltage to change the APD gain can be maintained constant with temperature changes, to ensure their normal work. APD multiplication gain is called the optimum avalanche gain, the formula is: M opt 2 + x 4 KT = q (I + I) xRL P db (3.5) (3.5), x is the excess noise factor, and its size depends on in the production of materials and production process of the APD. So that green laser pointer can not be used normally.
The best of APD multiplication gain depends on the incident power, the dark current, ambient temperature, and optoelectronic responsivity factors [12]. Figure 3.7 the temperature of the silicon APD - responsiveness - the bias curve from Figure 3.7 the temperature of the silicon APD - responsiveness - the bias curve can be seen, if you want to keep 30 Shandong University of Science and Technology bachelor's degree thesis phase-shift laser rangefinder receiver design the best gain of the circuit as the temperature changes, the APD bias voltage will change. Therefore, we must design temperature compensation circuit to control the bias voltage of the APD, the APD in a variety of temperature conditions can best multiplication gain, so that the receiving system to get the maximum signal to noise ratio. To ensure the safety and security of the user of  green laser pointer .
Temperature sensing chip MAX6613 Low-Voltage Analog Temperature Sensor MAX6613, a low operating voltage, low power consumption, small package size of the analog temperature sensor [13]. 1, as shown in Figure 3.8 and Table 3.1 shows the pin diagram of the MAX6613 chip and pin function: Figure 3.8 MAX6613 pin chart 3.1 MAX6613 Pin Pin 12345 symbols NC GND with the OUT VCC GND with function empty feet can be floating or grounded, the connected to the positive terminal of the output voltage of power and inversely proportional to temperature, and 5-pin connected a 0.1uF capacitor to ground-to-ground, the MAX6613 chip main features: 1.8 ~ 5.5V operating voltage, low quiescent current typical value of 7.5uA little effect on self-heating. It means that the battery of  green laser pointer can be charged and used again.
LM358 output side Vctl as a high-voltage generating circuit power input. Reference voltage can be calculated by the following formula: 33 Shandong University of Science and Technology bachelor's degree thesis phase-shift laser rangefinder receiver circuit V1 = (DC) * AB (3.10) in Figure 3.10, R42 = R45 = R47, the value of the reference voltage can also be calculated by the following formula: V1 = 5 R39 (R38 + R39) (3.11) the definition of V1 is to make the amplifier output voltage Vctl with hypertension circuit output voltage Voh difference between an integer multiple of. Virtual short by the amplifier, the principle of virtual off available, the same 1,2 point of the voltage, which can be drawn from the output voltage of the amplifier LM358: Vctl = (V1 + Vout) R40 (R35 + R40) of the previous section. Here will introduce the desk charger of green laser pointer .
High-voltage circuit in the output voltage Voh: Automatic gain control circuit AGC in practical applications, due to the close reflection of the laser pulse signal amplitude change is too large to receive the signal amplitude of the optical amplifier output corresponding change is too large, there may even be saturated distortion, another the interference of the laser, making the close measurement more difficult, if the receiving system in the automatic gain control (AGC) circuit can achieve zero blind from the measurement [7]. 3.5.1 Variable gain amplifier AD603 AD603 is a low-noise voltage-controlled gain a new op-amp, its transmission bandwidth up to 90MHz, the highest gain up to 51dB, the lowest-1ldB. The desk charger of  green laser    is firm.