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*H Bridge | *H Bridge | ||
− | An H bridge is an electronic circuit that causes current to flow in one direction or the other ( from a | + | An H bridge is an electronic circuit that causes current to flow in one direction or the other ( from a singel ended power supply ). Often used for motor control [[motor driver]]. |
It is an electronic double pole double throw switch. | It is an electronic double pole double throw switch. | ||
**[http://code.rancidbacon.com/Electronics] See Section on ''H-Bridge'' | **[http://code.rancidbacon.com/Electronics] See Section on ''H-Bridge'' | ||
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Discussion: | Discussion: | ||
− | I you have a lot of components that use the same voltage put them in parallel. This is how most lights in a house are wired. Each individual light can be turned on and off without changing the current or voltage in the other lights. With a bit of math you can show that the two resistors act like one resistor of value R = | + | I you have a lot of components that use the same voltage put them in parallel. This is how most lights in a house are wired. Each individual light can be turned on and off without changing the current or voltage in the other lights. With a bit of math you can show that the two resistors act like one resistor of value R = R1 + R2 /( R1 * R2 ). When you need a resistor of a different value than you have you can sometimes “make it up” using a parallel connection of resistors you do have. Two identical resistors in parallel are equivalent to one of half the resistance. A parallel circuit can have more than 2 resistors, there can be 3, 4, ... You can find out more about parallel circuits in the references. This circuit should be contrasted with the Series Circuit. Parallel circuits can also be used with other components, the equations vary, for capicators the capacitances add in a parallel circuit. |
More information: | More information: | ||
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Use this circuit when you want to convert AC to DC at significant current in order to provide DC power to another circuit component, it can be also used as a very low precision "precision rectifier". Basically similar circuits are sometimes used as demodulators for AM signals. | Use this circuit when you want to convert AC to DC at significant current in order to provide DC power to another circuit component, it can be also used as a very low precision "precision rectifier". Basically similar circuits are sometimes used as demodulators for AM signals. | ||
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+ | Circuit: | ||
+ | [[Image:pds.png | Pull Down and Switch ]] | ||
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+ | Where | ||
+ | *R_PULLDOWN resistor which normally keeps the output low ( ground ). | ||
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Discussion: | Discussion: | ||
There are many variations of this circuit, sometimes in combination with center tapped transformers, sometimes with multiple diodes ( as in bridge circuits ). | There are many variations of this circuit, sometimes in combination with center tapped transformers, sometimes with multiple diodes ( as in bridge circuits ). | ||
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+ | Links: | ||
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+ | * [] | ||
<!---------------------------------------------------------------------> | <!---------------------------------------------------------------------> | ||
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Use this circuit when you want to know the peak voltage of an AC of time varying DC voltage of just its absolute value. It typically differes from a power rectifier in that the circuit needs | Use this circuit when you want to know the peak voltage of an AC of time varying DC voltage of just its absolute value. It typically differes from a power rectifier in that the circuit needs | ||
its own source of power, it does not pass thru the power of the input voltage, it also differes in that the typical voltage drop of the power diode ( in the range of .5 to 2 volts ) is largely eliminated. This is a signal processing circuit. | its own source of power, it does not pass thru the power of the input voltage, it also differes in that the typical voltage drop of the power diode ( in the range of .5 to 2 volts ) is largely eliminated. This is a signal processing circuit. | ||
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+ | Circuit: | ||
+ | [[Image:pds.png | Pull Down and Switch ]] | ||
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+ | Where | ||
+ | *R_PULLDOWN resistor which normally keeps the output low ( ground ). | ||
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Discussion: | Discussion: | ||
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* [http://www.ti.com/lit/an/sboa068/sboa068.pdf PRECISION ABSOLUTE VALUE CIRCUITS By David Jones (520) 746-7696, and Mark Stitt] | * [http://www.ti.com/lit/an/sboa068/sboa068.pdf PRECISION ABSOLUTE VALUE CIRCUITS By David Jones (520) 746-7696, and Mark Stitt] | ||
* [http://i.stack.imgur.com/kUIO3.jpg Images] | * [http://i.stack.imgur.com/kUIO3.jpg Images] | ||
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This high side switch usually requires the base voltage of Q to be VPLUS_VDD plus the turn-on voltage of the transistor to turn all the way on. Another approach to the high side switch that requires a lower turn-on voltage is to use a PNP transistor as the switch. The base of the PNP is pulled up to VPLUS_VDD and connected to the collector of a small signal NPN transistor, Q2. Q2's emitter is connected to ground and its base is connected to the input signal through a current limiting resistor -- now the problem is that a high voltage is required to turn the switch off. | This high side switch usually requires the base voltage of Q to be VPLUS_VDD plus the turn-on voltage of the transistor to turn all the way on. Another approach to the high side switch that requires a lower turn-on voltage is to use a PNP transistor as the switch. The base of the PNP is pulled up to VPLUS_VDD and connected to the collector of a small signal NPN transistor, Q2. Q2's emitter is connected to ground and its base is connected to the input signal through a current limiting resistor -- now the problem is that a high voltage is required to turn the switch off. | ||
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== Transistor Emitter Follower == | == Transistor Emitter Follower == |