BD545-S

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The BD545-S is a silicon NPN, monolithic, low power, high gain limited, epitaxial base transistor.

These devices are designed for low speed, low power, medium to high current switching, or ground referenced audio or power amplifier input stages. Other applications include small signal amplifier, triggering, bridge circuits and oscillator circuits. This device is widely used in consumer electronics, automotive and instrumentation systems.

The recommended working principle of the BD545-S is based on the bipolar junction transistor (BJT). The BJT is a three-terminal device whose current-voltage relationship is based on two differently doped semiconductor regions, or regions of opposite polarity, called the emitter and base on two opposite sides of the base region and the collector on the other side.

The collector current is controlled by the base current, the base current is proportional to the amount of externally applied voltage. When the base-emitter junction is forward or biased beyond the maximum threshold, the collector current passes through the base-collector PN junction. This results in a current gain in the collector called the “beta” factor. The emitter current is proportional to the collector current.

The BD545-S transistor uses NPN type of bipolar vias to control current flow. A NPN bipolar device has a base (B) and a collector (C) interlevel connected with a P-type semiconductor layer. The emitter (E) is connected to a negative charge. Under normal conditions, the base-to-emitter junction is reverse biased, meaning the PN junction does not conduct.

When the voltage at the base is increased, the junction becomes forward biased, allowing current to flow from the emitter to the base. This in turn creates a positive charge on the base and a negative charge on the collector, which causes a current to flow from the collector to the base. The collector current is proportional to the base current and is termed the current amplification factor or Beta.

The BD545-S has a peak current gain (β) between 200 and 450 depending what bias and temperature conditions applied as well as other device parameters. Its saturation and cut-off voltages are 0.7V and 0.5V, respectively. It also has a low saturation-current when compared to most NPN transistors, and has a collector-emitter voltage rating of 80V, which makes it suitable for high frequency and current switch applications.

Because of its wide base-emitter voltage and high current gain, high power switch applications and motor drive transistors, the BD545-S can be used in a variety of applications. Its relatively low cost and ease of use have made it very popular in the industry.

The BD545-S is compatible with a variety of power and control designs and can be used to support a wide range of applications including amplifiers, switch drivers, motor controllers, power converters and many more. It is also highly suitable for use in audio amplifier, voltage regulator and voltage comparator circuits. The choice of the BD545-S can significantly reduce the cost of a power system and hence improve its performance, reliability and efficiency.

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