Bootstrapping

Bootstrapping alludes to a German legend about a Baron Münchhausen, who was able to lift himself out of a swamp by pulling himself up by his own hair. In later versions he was using his own boot straps to pull himself out of the sea which gave rise to the term .

Electronics

The term bootstrap has a number of meanings in electronics. In classical analog designs, a bootstrap circuit is an arrangement of components used to boost the input impedance of a circuit by using a small amount of positive feedback, usually over two stages. This was often necessary in the early days of bipolar transistors, which inherently have quite a low input impedance. The need for such arrangements has largely been alleviated by the use of modern field effect transistor designs, except when ultra-high input impedances are required. Note that because the feedback is positive, such circuits usually suffer from poor stability and noise performance compared to a circuit that doesn't bootstrap.

Related Topics:
Electronics - Analog - Input impedance - Feedback - Bipolar - Transistor - Field effect transistor

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Another meaning is in connection with the booting process of a computer or other complex system, where the underlying electronics must arrange for the orderly startup of the CPU and related electronics components. This is done long before the CPU is in a state where it can begin to execute software. Nowadays the bootstrap is coordinated by special integrated circuits that monitor the raw power supply and provide the relevant signals to enable the CPU and other chips accordingly.

Related Topics:
Booting - Computer - CPU - Integrated circuit - Power supply

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In a typical car alternator, a DC field current is required before the device can produce any output. Once running, a small portion of the output is fed back to keep the field alive — this can be seen as a form of bootstrapping. The initial priming current is usually obtained from the vehicle's battery — if the battery is totally flat the alternator won't produce any output voltage to recharge it even if the engine is started (by push starting for example) since it will be unable to bootstrap itself. However, in practice, a battery will usually have enough residual charge to avoid this.

Related Topics:
Alternator - DC - Battery

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