ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

What Are the Causes of Blown NPN Transistors

Updated on August 5, 2011

Issues of blown transistors


Transistors function as current regulators by using a small current introduced at the base to control a larger current flow between the collection and emitter. By varying the base current flow, or base voltage, the total current flow or voltage difference between the collector and emitter can be varied. The variation is known as “amplification factor.”

NPN transistors and their counterparts, PNP transistors, are types of bipolar-junction transmitters (BJT) that consist of three terminals – the base, collector, and emitter terminals. The difference between the PNP and NPN transistor is the direction in which current flows between the collector and emitter. In the case of an NPN transistor, it can be characterized as two diodes with a common anode, constructed of semi-conductor materials of two types, P and N. In operation, a small induced base current regulates a large emitter-to-collector current flow.

Transistors were developed in the late 1940s, and quickly replaced the bigger, slower, and more fragile vacuum tubes that were used prior to that time. Although transistors are incredibly rugged by comparison, they can still be damaged or destroyed (blown) if circuitry goes awry. Listed below are a few of the ways to blow an NPN transistor.

Excessive Voltage

Because transistors are sized based on a circuit’s operating voltage, any spike or large increase in the base system voltage will cause an NPN transistor to blow. This is because the transistor is designed to be a voltage storage container with a limited capacity, and will always be damaged when more voltage is pushed into the container than it was designed to hold or pass.

Thermal Load

Transistors must be kept cool to keep their semiconductor material from overheating and breaking down. If the material is allowed to begin breaking down due to heat, it will cause unnecessary resistance inside the transistor which will add to the heat load, and the likelihood of damage to the semiconductor material in the transistor becomes inevitable. Components and circuit boards must be kept cool at all times through the use of heat sinks and cooling fans.

Partial Operation

A bipolar-junction transmitter operates at its best when the collector-emitter flow is either turned completely on or completely off. Operation anywhere in between these two extremes will increase resistance in the component, and increased resistance is converted to heat in an electrical circuit. Left to operate at partial capacity for long periods of time will cause the transistor to overheat and fail, even when it is being properly cooled under normal operating conditions.

Excess Current Flow

Similar to the way a transistor responds to excessive voltage is the way it responds to excessive current flow. Overcurrent can occur as the result of a voltage spike, breakdown in the base current semiconductor material, or just by pushing more current through the system than it was designed. Short over-current bursts can be handled because they are dissipated as heat, but a long-duration over-current event will function with the mechanism similar to those above and cause the transistor to overheat and fail. In the same vein as overcurrent, current flow in the wrong direction will also blow NPN transistors. This can happen if a portion of the circuit’s polarity is reversed, or additional components are installed in the system which force current to flow opposite its expected path.


    0 of 8192 characters used
    Post Comment

    No comments yet.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)