The S8050 is a low voltage, high current NPN transistor that can be used as Class B push-pull amplifiers. S8050 is a bipolar junction transistor where electrons are major carriers, and holes are minor carriers. With a high DC gain of 300, S8050 finds its major application as an amplifier for boosting low signals, such as audio amplifiers. Before we analyze the S8050 datasheet, let’s discuss some basic principles behind its usage.
Using NPN transistor as Class B Push-Pull Amplifier
Amplifiers are used to power up the low power signal to a high power signal. One of the common applications is audio amplifiers such as loudspeakers and headphones. There are four different categories of amplifiers as follows:
- Class A amplifier
- Class B amplifier
- Class AB amplifier
- Class D amplifier
There are different ways to design amplifiers. Using transistors, such as the S8050, is the most popular one. S8050 is mainly used as Class B Push-Pull amplifiers.
Class B push-pull amplifiers make use of two complementary transistors (one NPN + one PNP) connected in a fashion with the voltage source and load, as shown below.
Both receive the same power signal but in opposite phases to each other. The NPN transistor gets forward biased during the signal’s positive half cycle, and the PNP transistor operates during the negative half cycle. As one pushes the current through the load and another does the opposite, it is called a push-pull amplifier.
Here, we can use an S8050 NPN transistor along with a complementary PNP transistor of the same operational characteristics to design a Class B push-pull amplifier.
While selecting a transistor for amplification, some of the key points to consider are:
- The maximum continuous output power: defines how loud the amplifier can be, often specified for different load impedances, distortion levels, and supply voltage configurations.
- Gain/Efficiency: ratio of the power turned into sound to the total power consumed by the amplifier. Low efficiency indicates loss of power in terms of heat. This may require a large heat sink which is often out of the question for audio boosting devices. The maximum efficiency of a Class B amplifier is 78.5%.
- Total Harmonic Distortion + Noise (THD+N): ratio of signal to noise and distortion in the amplifier output
With these basic knowledge supplements in mind, let’s explore essential elements of the S8050 datasheet.
S8050 Datasheet and Specifications
Here are some notable pieces of information from the S8050 datasheet.
- Maximum DC current gain: 300
- Power dissipation: 1 watt
- Base-emitter saturation voltage VBE(sat): 1.2 v
- Collector current: 1.5A
- Maximum Power: 2 Watt
- Base- Emitter Voltage ( VBE): 6V
- Collector-Emitter Voltage (VCE): 25V
- Collector-Base Voltage (VCB): 40
As the continuous electric c0llector current (IC) is 1.5v, we can not drive loads demanding more than 1.5v using this NPN transistor. The transistor can be biased by supplying current to the base but within its max limit. When the voltage across the base-emitter junction exceeds VBE(min) of 0.7V, the transistor operates in the forward biased zone (transistor gets switched ON). The transistor is in an active region and we can use it for amplification. We can bias the output current by changing the input supply voltage. The level of amplification depends on the gain of the transistor.
The maximum DC gain value is 300. Under forward biased condition, the output current can get amplified up to 300 times that of the input current until the transistor is in the forward biased condition.
Once it is fully biased, the transistor enters into the saturation region. There, it can drive a max 1.5 amp load at a max collector emitter voltage VCE(max) of 25v and max collector base voltage VCBO(max) of 40v. In the absence of base current, the transistor enters the cut-off region and remains switched off.
S8050 alternatives
A few NPN transistors have equivalent functionalities to the S8050 transistor:
- 2N7051
- 2SC3726
- 2SC4145
- 2SD1146
- BTN8050A3
The above models were selected keeping the following factors in mind.
- Transistor type: NPN
- Package type: TO-92
- Low power consumption
- VCB > 40V
- VCE > 25V
- VEB > 6V
- IC > 1.5A
- HfE > 85
- Tj > 150 C
However, before choosing any of these transistors, it is imperative to check for individual parameters from their respective datasheets to ensure a safe design.
Packaging
The S8050 comes in a standard TO-92 package. The compact epoxy packaging comes with space-saving attributes. The height of the pins is around 15mm. The pin numbering is from left to right with the flat surface of the pin facing towards you. The pin layout is as follows:
| Pin Number | Connections |
| 1 | Emitter |
| 2 | Base |
| 3 | Collector |
The S8050 datasheet shows all you need to know about the package dimension for designing purposes. Along with the package dimension, you may also need accurate footprints, ECAD/MCAD models and application notes to get started.
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