TREE

A photo diode is a PN junction or PIN structure that when light reaches the junction, it excites an electron thereby creating a free electron positively charged. This mechanism is also known as the photoelectric effect, common in transistors, diodes and ICs are made ​​of semiconductors, and contain PN junctions. Almost all of the potentially active constituents are a photo diode and may be used as a photo sensor. The PN junction needs to be exposed to light, so to use a semiconductor diode as a light bulb must have a transparent glass, these diodes with  these characteristics can be used to measure the light intensity.  Circuit diagram of a light intensity meter with diode.   a test circuit diode light sensor List of components: D1 1n148 or any other photo-sensitive element T1, T2 BC548 or similar C1 680n R1 2M Above this circuit that is very popular, it works with LEDs, photodiodes and photo-resistors. V is a voltmeter which can be a multimeter.

This solid-state push-pull single-ended Class A circuit is capable of providing a sound comparable to those valve amplifiers, delivering more output power (6.9W measured across a 8 Ohm loudspeaker cabinet load), less THD, higher input sensitivity and better linearity. Voltage and current required for this circuit are 24V and 700mA respectively, compared to 250V HT rail and 1A @ 6.3V filament heating for valve-operated amplifiers. The only penalty for the transistor operated circuit is the necessity of using a rather large Heatsink for Q2 and Q3 (compared to the maximum power delivered).In any case, the amount of heat generated by this circuit can be comparable to that of a one-valve amplifier. An optional bass-boost facility can be added, by means of R5 and C5. 5 Watt Class-A Audio Amplifier Circuit diagram Parts: P1 = 47K R1 = 100K R2 = 12K R3 = 47K R4 = 8.2K R5 = 1.5K R6 = 2.7K R7 = 100R R8 = 100R R9 = 560R-1/2W R10 = 1R-1/2W Q1 = BC560 Q2 = BD439 Q3 = BD439 C1 = 10uF-63V C2 = 10uF-6...

T his t sink in high power circuits. In this temperature indicator, diode voltage drop in ambient temperature is used as reference level. Temperature is measured by a transistor mounted on a radiator or near power transistor controlled.T1 temperature sensor and voltage to the base - emitter is compared, through potentiometer P1, with the common point of reference in its D1 and R1. Temperature Indicator circuit diagram Transistor remains blocked as long as temperature remains below a certain level, which is set to P1. Base-emitter voltage of transistor will decrease by about 2mV for a temperature increase of about 1 ° C. When the emitter voltage of transistor voltage falls below the cursor P1, the transistor will go into conduction and D2 will light.The values of R1 and R2 are voltage dependence of Ub and relationships can be calculated: R1 = [(Ub - 0.6) / 5] k, R2 = [(Ub - 1.5) / 15] k