Varactor (Varactor Diodes) as a special diode. When the applied forward bias voltage, a large current is generated, PN (positive and negative) junction depletion region is narrowed, the capacitance increases, resulting in diffusion capacitance effect; when the applied reverse bias, glass diodes, will generate transition capacitance effect. But when applied forward bias leakage current will be generated, so the applications are supplied to a reverse bias voltage. Also known as varactor diodes varicap, based on changes in the voltage provided to the semiconductor junction capacitance changes. That is, as a variable capacitor, can be applied to the FM tuner and TV tuner resonant circuit and the FM modulation circuit. The most important characteristic of the diode is conductive in one direction. In the circuit, the current can only flow into the diode from the positive and negative outflow. Forward characteristic in an electronic circuit, the diode cathode connected to the high potential side, diodes, the negative pole in the low potential side, 1N5248B diodes, will be turned, 1N4749A diode, this connection is called forward bias . Must state, when applied across the diode forward voltage is small, the diode is still not turned on, flows through the diode forward current is very weak. Only when the forward voltage reaches a certain value (this value is referred to as "threshold voltage", also known as the "dead zone voltage", germanium tube is about 0.1V, silicon tube of about 0.5V) after being turned straight to the diode. After the turn-on voltage remains substantially constant across the diode (germanium tube is about 0.3V, silicon tube of about 0.7V), the diode is called "forward voltage drop." Reverse characteristic in an electronic circuit, connected to the anode of the diode of the low potential side, a negative electrode connected to the high potential side, when the diode is almost no current flows through the diode in the OFF state at this time, this connection is called a reverse bias. When the diode is reverse biased, there will still be a weak reverse current flows through the diode, known as leakage current. When the reverse voltage across the diode increases to a certain value, the reverse current increases dramatically, the diode will lose one-way electrical properties, this state is called a diode breakdown. Diode voltage drop: a silicon diode (non-light emitting type) forward voltage drop of 0.7V, germanium tube forward voltage drop of 0.3V, light-emitting diode forward voltage drop will vary with different emission colors. There are three main colors, the specific reference values ??drop as follows: red light-emitting diode voltage drop 2.0--2.2V, yellow light-emitting diode voltage drop of 1.8-2.0V, a green light-emitting diode voltage drop of 3.0-3.2V, normal Rated current emits light approximately 20mA. _ The integrity _1N4749A diode diode provided by Qingdao integrity Technology Co., Ltd. _ The integrity _1N4749A diode diode is Qingdao integrity Technology Co., Ltd. (www.qdjcx.com) this year introduced a new upgrade, the above picture is for reference only, please call Tel picture on this page or to obtain the latest information Contact: Mr. Yang.