Autosave: 2024-07-04 07:00:04

zk/Breadboards.md

@@ -29,4 +29,4 @@ The contact holes on the outer edges of the breadboard, designated by numbers
 You will typically use the positive bus strip on one side for the voltage source
 and the negative bus strip on the other side for the ground outlet.
 
-## Related notes
+

zk/Push_buttons.md

@@ -17,11 +17,20 @@ pairs.
 To create a breakable circuit we would connect a signal-in cable to the top left
 at row 23 and a signal-out cable to the bottom-right at row 25.
 
+![Push button legs diagram](../img/push-button-legs.png)
+
+_The correct use of a push button where the button breaks the circuit_
+
+![](../img/correct_push_button.jpg)
+
 To override the switch functionality and just have the button work as a
 connector we would connect the signal-in to the row 23 input and the row 23
 output.
 
-![Push button legs diagram](../img/push-button-legs.png)
+_The push button being used as simple connector which does not break the
+circuit:_
+
+![](../img/incorrect_push_button.jpg)
 
 ## Related notes
 

zk/Transistors.md

@@ -7,103 +7,58 @@ tags:
 
 # Transistors
 
-In the discussion of
-[digital circuits](Digital_circuits.md)
-we noted that a digital circuit requires that electrical phenomena be treated as
-discrete rather than continuous values. Although a given voltage at a point in
-the circuit can vary widely, in order to represent the binary states of 'on' and
-'off' we need it to remain fixed within certain narrow parameters.
-Typi>understanding the concept and then with transistors which are what are
-actually used in computers.
+A digital circuit requires that electrical phenomena be treated as discrete
+rather than continuous values.
 
-## Implementing binary logic with mechanical switches
+Although a given voltage at a point in the circuit can vary widely, in order to
+represent the binary states of 'on' and 'off' we need it to remain fixed within
+certain narrow parameters. This is achieved with transistors.
 
-An electrical switch is inherently binary. When the switch is on, it acts like a
-simple copper wire through which current flows freely. When the switch is off,
-it acts like an open circuit and no current can flow.
-
-We can combine switches in a circuit to create analogs to logic gates.
-
-![](/img/switch-and-gate.png)
-
-In the example above a simple AND gate is implemented with switches. Each switch
-is a conjunct and the current only flows if both switches are on, closing the
-circuit.
-
-![](/img/switch-or-gate.png)
-
-In the example above is a circuit implementing an OR gate. The current flows
-just if one of the switches are on or if both of the switches are on but not if
-both switches are off.
-
-## Transistors
-
-In real digital circuits, mechanical switches would be totally impractical. The
-number of switches required is too numerous and we need to be able to connect
-and interconnect the output of many circuits together. The output of one circuit
-needs to be fed into another and there is no way to do this with switches.
-
-Thus instead of switches, modern digital circuits use transistors, a special
-electrical component that controls the flow of current in the manner of a switch
-where the 'off' and 'on' states are represented by
-[voltage](Voltage.md) values within
-set parameters.
+Transistors are an electrical component that is capable of controlling the flow
+of current in the manner of a switch where the 'off' and 'on' states are
+represented by [voltage](Voltage.md) values within set parameters.
 
 There are different types of transistors but the simplest for the purposes of
 explanation are **bipolar junction transistors**.
 
-![](/img/transistor-diag.svg)
+![BJT transistor terminals](../img/bjt-terminals.jpg)
 
-A transistor works as follows: applying a small amount of current at the base
-allows a larger current to flow from the collector to the emitter. Relating this
-back to switches, applying current to the base is like turning the switch on.
-Removing this current is like turning the switch off.
+The pins:
 
-The diagrams below show a transistor being used in a circuit to create 'on' and
-'off' switch states alongside a switch based circuit.
+- C: collector
+- B: base
+- E: emitter
 
-![](/img/transistor-off.png)
+Applying a small amount of current at the base allows a larger current to flow
+from the collector to the emitter. Applying current to the base is like turning
+the switch on. Removing this current is like turning the switch off.
 
-![](/img/transistor-on.png)
+This happens because of how current and voltage interact in a transistor. The
+small base current controls the larger collector-emitter current through a
+process called current amplification.
 
-- $V^{in}$ is the voltage that electrically controls the switch-as-transistor
-- $V^{out}$ is the voltage we want to control: it will be high when the
-  transistor is in the 'on' state and low otherwise
-- $V^{cc}$ stands for "common collector" and is the positive supply voltage
-  appliced to the collector terminal is "on".
+This happens because of how voltage works. Voltage is the potential difference
+between two terminals in a circuit. A high voltage increases the flow of current
+whereas low voltage restricts or reduces it.
 
-When the voltage at the base is low (in the diagram it is grounded to ensure
-this) no current flows from the c We recall that voltage is the potential
-difference between two points or terminals in a circuit. High voltage increases
-the flow of current, low voltage restricts or reduces it.
-
-When the voltage at the base is high a current flows from the collector to the
-emitter and the transistor is "on".
-
-When the voltage at the base is low (in the diagram it is grounded to ensure
-this) no current flows from the collector to the emitter and the transistor is
-"off".
+It follows from this that when the voltage at the base is high, a current flows
+from the collector to the emitter and the transistor is "on". Whereas when the
+voltage at the base is low no current flows from the collector to the emitter
+and the transistor is "off".
 
 ## Transistors and logic gates
 
-With the basic element of the transistor established, we can combine transistors
-to create logic gates. A logic gate is a combination/sequence of transistors
-where the logical function is represented by the characteristic input and output
-voltages.
+We can combine transistors to create logic gates. A logic gate is a combination
+of transistors arranged such that the logical function is embodied by the
+characteristic input and output voltages to the transistor.
 
-For example to create an
-[AND](Logic_gates.md#and-gate) gate
-we would have two voltage inputs going into two transistors that are connected
-in sequence. The two transistors create a continuous line going from the
-collector of one to the emitter of the other. If either voltage input is low
-then the voltage of the combined line is low (equivalent to the circuit being
-broken) and there is no current flowing.
+For example to create an [AND](Logic_gates.md#and-gate) gate we would have two
+voltage inputs going into two transistors that are connected in sequence. The
+two transistors create a continuous line going from the collector of one to the
+emitter of the other. If either voltage input is low then the voltage of the
+combined line is low (equivalent to the circuit being broken) and there is no
+current flowing.
 
 ![](/img/and-transistor.png)
 
-Below, an
-[OR](Logic_gates.md#or-gate) has been
-constructed with transistors. If a voltage is applied to the base of either
-transistor, the current reaches the V-out terminal.
-
-![](/img/or-transistor.svg)
+// Add example of OR gate created with transistors