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S8550 Transistor Data
Key transistor data for the S8550 PNP audio output transistor including key electrical parameters, pinout, package type and many other key transistor datasheet details.
The S8550 is described as an PNP epitaxial silicon transistor designed for class B push-pull output stages up to 2 watts for portable radios.These transistors are complementary to the S8050, making them deal for use in a push-pull class B output stage.
The transistors can handle a collector current up to 1.5A, despite being encapsulated in a TO92 package.
Key details and performance parameters for the S8550 transistor.
| S8550 transistor datasheet parameters & data |
|
|---|---|
| Parameters | Details |
| Transistor type | NPN silicon |
| Package type | TO92 |
| VCBO max (V) | -40 |
| VCEO max (V) | -25 |
| VEBOmax (V) | -6 |
| VCEsat (V) | -0.28 V typ, -0.5max @ I |
| IC max (mA) | -1500 |
| TJ Max °C | 150 |
| PTOT mW | 1 |
| fT min (MHz) | 100 MHz min and typically 200 MHz |
| COB | 15pF |
| hFE | 85 - 300 see classifications below. |
| IC for hfe | 100mA |
| Similar / equivalents | |
Outline:
Pinout:
S8550 leaded hFE classifications
| S8550 hFE classifications |
|||
|---|---|---|---|
| Classifications | S8550B | S8550C | S8550D |
| hFE | 85 ~ 160 | 120 ~ 200 | 160 ~ 300 |
S8550 SMD version
| S8550 transistor datasheet parameters & data |
|
|---|---|
| Parameters | Details |
| Transistor type | PNP silicon |
| Package type | SOT23 |
| VCBO max (V) | -40 |
| VCEO max (V) | -25 |
| VEBOmax (V) | -6 |
| IC max (mA) | 500 |
| TJ Max °C | 150 |
| PTOT mW | 300 |
| fT min (MHz) | 100 MHz min |
| COB | 9pF |
| hfe | 120 - 350 see below |
| IC for hfe | 50mA |
| Similar / equivalents | |
Outline & pinout:
S8550 SMD hFE classifications
| S8050 SMD hFE classifications |
||
|---|---|---|
| Classifications | S8550L | S8550H |
| hFE | 120~200 | 200~350 |
Explanation of transistor parameters
| Parameter | Explanation |
|---|---|
| VCBO Max | Maximum collector-base voltage with emitter open circuit . |
| VCEO Max | Maximum collector-emitter voltage with base open circuit. |
| VEBO Max | Maximum emitter-base voltage with collector open circuit. |
| VCEsat (included where applicable) | The voltage drop across the collector-emitter when the transistor is fully saturated (acting as a closed switch). |
| IC Max | Maximum collector current. |
| Parameter | Explanation |
|---|---|
| TJ | Maximum junction temperature. |
| PTOT Max | Maximum device dissipation normally in free air at 25°C unless other conditions indicated. |
| fT Min | Minimum cutoff frequency at which the current gain in a common emitter circuit falls to unity. |
| COB Max | Maximum collector capacitane, normally measured with emitter open circuit. |
| hFE | DC current gain for HFE at IC. [Note hfe is the small signal gain and although this may be slightly different, the transistor current gain will vary considerably from ne transistor to the next of the same type.] |
| PTOT Max | Maximum device dissipation normally in free air at 25°C unless other conditions indicated. |
These are the main transistor parameters that have been included in our list. There are others, but these help quantify the main elements of the performance of the transistor.
Please note, that the data given is the best estimate we can give within a tabulated summary of this nature. Parameters also vary between manufacturers. Electronics Notes cannot accept any responsibility for errors, inaccuracies, etc, although we do endevaour to ensure the data is as accurate as possible.
Notes and supplementary information
• Availability & sources
The device is available from a number of stockists and electronic component distributors.
• S8550 further details
The S8050 was originally manufactured by a number of tier 1 companies including Fairchild, but now they are widely available in transistor selection kits manufactured by unknown manufacturers int he Far East.
While these much cheaper alternatives are ideal for many home construction applications, they are not suitable for mainline manufacturing because of their unknown reliability and supply chain.
The S8550 is ideal for many general purpose applications as it has a high gain and general capability.
• S8550 hFE ranges
The S8550 has suffixes added to the part number: S8550B, S8550C, and S8550D to indicate the range of current gain.
| S8550 hFE classifications |
|||
|---|---|---|---|
| Classifications | S8550B | S8550C | S8550D |
| hFE | 85 ~ 160 | 120 ~ 200 | 160 ~ 300 |
• Typical output stage
The S8550 is a PNP transistor which is complementary to the S8050 and this makes theis pair of transistors ideal for use in a class B (push-pull) low power audio output stage.One of the key applications mentioned in the datasheet for the S8050 was that of being used in a class B or push-pull output stage for a transistor radio.
Push pull output stages are far more efficient when compared to class A ones and this means that smaller transistors with lower maximum heat dissipation figures can be used.
Although the S8550 is specified as having a relatively high dissipation figure, it is only contained within a plastic TO92 case and therefore it is wise not to approach, and certainly not exceed the maximum dissipation figure.
The circuit of an typical generic push-pull or class B output stage is given in the diagram. It uses an NPN and a PNP transistor, each handling opposite sides of the waveform.
In terms of its operation, the input waveform is applied to the base electrodes of both transistors, TR1 and TR2 via the capacitors C1 and C2. It is necessary to apply it directly to the base of each transistor using two capacitors as shown to ensure the signal is at an appropriate level.
The resistor chain consisting of R1, R2 and R3 provide the biasing for the transistors holding them at their turn on point, so that opposite halves of te audio cycle are covered by the two transistors with only minimal cross-over distortion.
The capacitor C3 is required because most transistor radios using these small output transistors would only have a single voltage rail, i.e. the positive supply and ground.
Written by Ian Poole .
Experienced electronics engineer and author.
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