Difference between revisions 141901230 and 141901232 on dewiki

'''Diode logic''' or '''Diode-resistor logic''', is a circuit style that uses [[diode]]s to construct [[Boolean logic|Boolean]] [[logic gate]]s for [[electrical circuit|circuits]]. Only non-[[inverter (logic gate)|inverting]] functions may be implemented, so it is not a complete [[logic family]]. Furthermore, such circuits are non-restoring: the output of any gate is further from a perfect ''0'' or ''1'' than(contracted; show full)

The circuit of a two-input gate is shown opposite. The cathode of every diode is connected to the output at Node 1. A resistor connects Node 1 to ground (low voltage, Node 2), and the remaining ''n'' nodes are the inputs.

Whenever a logic ''1'' is present at the anode of a diode, it forward-biases that diode, causing it to conduct. The input can then induce a current at the output through the resis
itor, to cause the output voltage to be closer to ''1''.

If a logic ''0'' is present at the anode of every diode, they are all reverse-biased and the resistor drives node 1 low.

==AND gate construction==
[[image:Diode-AND2.png|thumb|right|Diode AND gate: example with two inputs]]
To construct an [[AND gate]] with ''n'' logic inputs, the following components are required:
* ''n'' diodes
* a [[resistor]] of much more resistance than anything you wish to turn the gate off

An example circuit is shown on the right. The resistor connects Node 1 to the supply voltage at Node 2. Nodes 4 and 5 are the inputs. The output is obtained at Node 1. 

If a logic ''1'' is present at the cathode of every diode, then they are all reverse biased, remaining in a high-impedance state, and Node 1 is held high by the power supply through the resistor. 

If a logic ''0'' is present at any input, it forward-biases that diode and may hold Node 1 low through the diode.

==References==
*[http://www.play-hookey.com/digital/electronics/dl_gates.html Diode logic]
* [http://www.robotroom.com/Joystick2.html "Joystick Controller: Using Diodes to Create OR Circuits"] by David Cook

[[Category:Logic families]]

[[id:Logika dioda–resistor]]