BD645 Transistor Pinout, Equivalents, Applications, Features, Advantages, Disadvantages and More
BD645 is an NPN Darlington transistor of BD64x series. This series is designed to be used in audio frequency applications and is also good for high current gain applications and can also be used as complimentary audio frequency push pull output stages. This article contains BD645 transistor pinout, equivalents, applications, features, advantages, disadvantages and other details.
Understanding the BD645 Transistor:
As discussed BD645 is an NPN Darlington transistor. A Darlington transistor looks the same as a BJT transistor from outside but internally it contains two BJT transistors that are connected in a special way that increases its gain to a great extent, this special way of connecting two transistors is called Darlington pair, like other Darlington transistors BD645 looks like a BJT from outside, but internally there are two NPN transistors. Each one has three layers inside which are N-type / P-type / N-type, same as the normal BJT transistor. Mostly, in these type of transistors, the collectors of both internal transistors are connected to the transistor’s mounting base.
While BD645 is designed to be used in audio frequency, high gain and push pull amps output stages but can also be used in variety of other related applications, such as switching circuits, motor drivers, led drivers etc. More applications can be found under the applications heading below.
Pin Configuration:
The pin configuration of the transistor are as follows:
Pin1 is the Base pin: The Base pin is the first pin of the transistor, the current flow from collector to emitter can be controlled through this pin.
Pin2 is the Collector pin: The Collector drives the output load of the transistor.
Pin3 is the Emitter pin: The current flows from the collector to the emitter through the base.
PNP Complementary:
PNP Complementary of BD645 is BD646
Features and Specifications of the Transistor:
- Package Type: TO-220
- Transistor Type: NPN Darlington
- Max Collector Current(IC): 8A
- Max Collector-Emitter Voltage (VCEO): 60V
- Max Collector-Base Voltage (VCBO): 80V
- Max Emitter-Base Voltage (VEBO): 5V
- Max Collector Power Dissipation (Pc): 62.5mW
- Minimum DC Current Gain (hFE): 750
- Max Storage & Operating temperature: -55 to +150 Centigrade
Replacement & Equivalent
TIP140T, TIP132, TIP131, TIP102, TIP100, BDX53A/B, BDX33A/B/C, BDW73A/B/C, BDW41A/B, BDT65/A/B/C, BD901, BD897, BD649, 2SD1830, 2N6044, 2SD1277, 2SD1192, 2N6530, 2N6387.
Advantages & Disadvantages of Using 2SC5763:
Here we will discuss the advantages and disadvantages of BD649 Darlington transistor.
Advantages:
A High Gain Transistor: The minimum DC current gain is 750, a high DC current gain transistor requires less base current to drive a load.
Upto 60V Voltage Handling Capability: It can drive a load of upto 60V which makes it suitable to drive a variety of moderate voltage applications.
Availability of Complementary Transistor: Its complimentary pair is also available so you can pair it with its complimentary for good results.
Good Collector Current of Upto 8A : The maximum collector current of 8A is enough to drive variety of small to medium power loads in an application.
Low Saturation Voltage: The low saturation voltage make sure to drop minimum voltage in ON state, which increases the efficiency of the transistor.
Disadvantages:
High VBE : The high VBE makes this transistor not ideal for low voltage circuits.
Only 8A Collector Current: Although the maximum collector current of 8A is good to drive low to medium power loads, it cannot driver high power loads.
Slow Switching Speed: Darlington transistor are not high speed switching transistors due to which they cannot be used in high speed switching applications.
Saturation Voltage of 2 to 2.5V: Due to their high saturation voltage the Darlington transistors are not ideal for portable and battery operated applications because they cause some power loss.
Applications:
Push-Pull Amplifiers
Switching Circuits
Audio Amplifiers
DC Motor Drivers
Relay Drivers
Battery Chargers
Voltage Regulators
Power Supply Circuits
Conclusion:
BD645 is an NPN Darlington transistor designed AF push pull output stages and also good to be used for audio frequency applications and high current gain applications. The transistor can drive maximum load of 60V and is suitable for low to medium voltage loads. The maximum collector current is 8A which is also ideal for small to medium current loads. The complimentary pair of the transistor is also available and the maximum collector power dissipation is 62.5W but on the other hand the transistor also has some limitations such as low switching speed (The Darlington transistors are not high speed switching transistors), the maximum collector current is ideal for low to medium current load but for high current loads you have to look for other high current transistor options. But if you are looking for a Darlington transistor that high gain and good for push pull output stage or a Darlington transistor for general purpose applications then BD645 can be a good choice.
Datasheet:
To download the datasheet just copy and paste the below link in your browser.
https://www.alldatasheet.com/datasheet-pdf/view/624040/NJSEMI/BD645.html
