165:. When the low-side N-FET is on, current from the power rail (V+) flows through the bootstrap diode and charges the bootstrap capacitor through that low-side N-FET. When the low-side N-FET turns off, the low side of the bootstrap capacitor remains connected to the source of the high-side N-FET, and the capacitor discharges some of its energy driving the gate of the high-side N-FET to a voltage sufficiently above V+ to turn the high-side N-FET fully on; while the bootstrap diode blocks that above-V+ voltage from leaking back to the power rail V+.
52:(by shifting both its positive and negative supply rail) in order to increase its output voltage swing (relative to the ground). In the sense used in this paragraph, bootstrapping an operational amplifier means "using a signal to drive the reference point of the op-amp's power supplies". A more sophisticated use of this rail bootstrapping technique is to alter the non-linear C/V characteristic of the inputs of a JFET op-amp in order to decrease its distortion.
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resistance, so this scheme is only used where there is a steady pulse present. This is because the pulsing action allows for the capacitor to discharge (at least partially if not completely). Most control schemes that use a bootstrap capacitor force the high side driver (N-MOSFET) off for a minimum time to allow for the capacitor to refill. This means that the
193:, the control circuits are powered from the output. To start the power supply, a leakage resistance can be used to trickle-charge the supply rail for the control circuit to start it oscillating. This approach is less costly and simpler than providing a separate linear power supply just to start the regulator circuit.
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Within an integrated circuit a bootstrap method is used to allow internal address and clock distribution lines to have an increased voltage swing. The bootstrap circuit uses a coupling capacitor, formed from the gate/source capacitance of a transistor, to drive a signal line to slightly greater than
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size reduction (there are other benefits as well). However, using nMOS devices in place of pMOS devices means that a voltage higher than the power rail supply (V+) is needed in order to bias the transistor into linear operation (minimal current limiting) and thus avoid significant heat loss.
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is a voltage-controlled device which, in theory, will not have any gate current. This makes it possible to utilize the charge inside the capacitor for control purposes. However, eventually the capacitor will lose its charge due to parasitic gate current and non-ideal (i.e. finite) internal
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technique for providing a low-frequency pole inside an integrated circuit. To minimize the size of the necessary capacitor, it is placed between the input and an output which swings in the opposite direction. This bootstrapping makes it act like a larger capacitor to ground.
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feedback may alternatively be used to bootstrap an input impedance, causing the apparent impedance to be reduced. This is seldom done deliberately, however, and is normally an unwanted result of a particular circuit design. A well-known example of this is the
87:, which inherently have quite a low input impedance. Because the feedback is positive, such circuits can suffer from poor stability and noise performance compared to ones that don't bootstrap.
209:, providing bias voltages that exceed the power supply voltage. Emitter followers can provide rail-to-rail output in this way, which is a common technique in class AB audio amplifiers.
98:, in which an unavoidable feedback capacitance appears increased (i.e. its impedance appears reduced) by negative feedback. One popular case where this
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of a transistor above the power supply rail. The same term has been used somewhat more generally for dynamically altering the operating point of an
158:). Due to the charge storage characteristics of a capacitor, the bootstrap voltage will rise above (V+) providing the needed gate drive voltage.
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will always need to be less than 100% to accommodate for the parasitic discharge unless the leakage is accommodated for in another manner.
134:) applied to the gate in order to turn on. Using only N-channel MOSFET/IGBT devices is a common cost reduction method due largely to
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Graeme, Jerald (1994). "Op-amp distortion measurement bypasses test-equipment limitations". In
Hickman, Ian; Travis, Bill (eds.).
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A bootstrap capacitor is connected from the supply rail (V+) to the output voltage. Usually the source terminal of the N-
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of the amplifier. When applied deliberately, the intention is usually to increase rather than decrease the impedance.
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circuit is one where part of the output of an amplifier stage is applied to the input, so as to alter the input
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of a circuit. Usually it is intended to increase the impedance, by using a small amount of positive
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AC amplifiers can use bootstrapping to increase output swing. A capacitor (usually referred as
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designs, a bootstrap circuit is an arrangement of components deliberately intended to alter the
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allowing for efficient management of stored energy in the typically inductive load (See
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A bootstrap circuit is often used in each half-bridge of an all-N-MOSFET
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551:"How the bootstrap load made the historic Intel 8008 processor possible"
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IEEE Standard 100 Authoritative
Dictionary of IEEE Standards Terms
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Bootstrap capacitors C1 and C2 in a BJT emitter follower circuit
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circuits, bootstrapping is commonly used to mean pulling up the
436:"Bootstrap Circuitry Selection for Half-Bridge Configurations"
393:"Bootstrapped IC Substrate Lowers Distortion in JFET Op Amps"
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where part of the output of a system is used at startup.
205:) is connected from the output of the amplifier to the
346:"Bootstrapping your op amp yields wide voltage swings"
230:use that 2-transistor "bootstrap load" circuit.
413:(2nd ed.). Focal Press. pp. 136–142.
269:(7th ed.). IEEE Press. 2000. p. 123.
481:. Cambridge University Press. pp. 190–1.
222:Some all-pMOS integrated circuits such as the
507:"The New Methodology for Random Logic Design"
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477:Dally, William J.; Poulton, John W. (1998).
344:King, Grayson; Watkins, Tim (May 13, 1999).
323:(2nd ed.). Springer. pp. 210–211.
398:. Analog Devices application note AN-232.
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242:(creating a virtual infinite impedance)
123:needs a significantly positive charge (
370:. Butterworth-Heinemann. p. 205.
454:Demystifying switching power supplies
248:, initial program load for a computer
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14:
16:Startup technique in electronics
22:is a technique in the field of
549:Shirriff, Ken (October 2020).
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317:Pelgrom, Marcel J.M. (2012).
368:The EDN Designer's Companion
320:Analog-to-Digital Conversion
479:Digital systems engineering
240:Miller theorem applications
214:Digital integrated circuits
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191:switch-mode power supplies
185:Switch-mode power supplies
452:Mack, Raymond A. (2005).
411:Small Signal Audio Design
296:. Springer. p. 319.
293:CMOS Logic Circuit Design
290:Uyemura, John P. (1999).
102:done deliberately is the
434:Diallo, Mamadou (2018).
456:. Newnes. p. 121.
111:Driving MOS transistors
571:Electronic engineering
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409:Douglas Self (2014).
219:the supply voltage.
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50:operational amplifier
529:"The Bootstrap Load"
441:. Texas Instruments.
146:is connected to the
203:bootstrap capacitor
150:of a recirculation
104:Miller compensation
527:Faggin, Federico.
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420:978-1-134-63513-9
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303:978-0-7923-8452-6
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355:: 117–129.
253:References
228:Intel 8008
224:Intel 4004
179:duty cycle
35:impedance
31:bootstrap
565:Category
234:See also
226:and the
163:H-bridge
91:Negative
78:feedback
534:June 3,
512:June 3,
246:Booting
148:cathode
82:bipolar
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170:MOSFET
144:MOSFET
129:> V
117:MOSFET
42:MOSFET
439:(PDF)
396:(PDF)
349:(PDF)
152:diode
115:An N-
536:2017
514:2017
483:ISBN
458:ISBN
415:ISBN
372:ISBN
325:ISBN
298:ISBN
271:ISBN
174:IGBT
121:IGBT
353:EDN
189:In
136:die
68:In
29:A
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132:th
127:GS
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