2 diodes, either annode to annode (NPN) or cathode to cathode (PNP)
Operation in switching circuits
Use the base-emitter circuit to control the emitter-collector circuit
A photocell changes its resistance based on the amount of ambient light. A tiny photocell -for example- can control whether electricity flows or not based on how bright the area is. Or whether or not an LED is shining on it. You may want to do this to completely isolate two different circuits.
Output circuits of a small Arduino or
Rasberry Pi can control high powered LEDs or Relays. Inegrated Circuits such as small computers are very delicate and can only switch up to 10 ma (10/1000 or 1/100 of an ampere). But an LED requires 20 ma.
Operation in amplification circuits
But the tricky part is that one can be used to control the other. And since the other can have a lot more power going through it than the first, you can use a tiny voltage change to make a large voltage change by a large quanitty. Here, for example, is a very simple audio amplifier circuit.
So a tiny base-emitter voltage can control an enormous emmitter-collector circuit so you can amplify a microphone signal to use in making a 1,000 watt FM transmitter.
Field Effect Transistor (FET, JFET)
A Juction Field Effect Transistor has a Source, gate, and drain
Closest in general operating characteristics to a Vaccum Tube
MOSFET - Metal Oxide Semiconductor Field Effect Transistor
Operation and unique applications;
UJTs "A unijunction transistor (UJT) is a three-lead electronic semiconductor device with only one junction that acts exclusively as an electrically controlled switch. The UJT is not used as a linear amplifier"(Wikipedia)
Check the AC voltage from a wall outlet VERY CAREFULLY on the AC Volts 200 volt scale
Check diodes and resistors
Check fuses and light bulbs using the resistance scale. If a fuse or light is good, it'll read zero ohms. If it's broken, it'll read INF or infinite ohms.
How to check a transistor
There are only 4 ways to preserve food in a wharehouse
Smoke (Lox, etc)
Sugar does everything to each organ in the human body that alcohol doess (with the exception of the brain; sugar and alcohol make brains do different things, everything else, they do the same thing to).
Cocaine comes from a plant which is the only source of vitimane C (To prevent people dying of Scurvy) in the high altitude mountains in Bolivia. They chew on the leaves or make it into a tea. It's also very restorative to your musculature.
Introductory Radio Theory
Amplifiers -- makes a signal louder. Makes an RF signal bigger.
Attenuators -- makes a signal quiter or smaller. Resistors can attinuate.
Oscillators -- an Oscillator is merely an amplifier specifically designed with its output coupled to (connected to) its input so that it feeds back upon itself rather like when you twang your electric guitar too close to the speaker. Oscillators are designed to produce sustained pure sine waves. In fact, the only ways to make AC is either with an Alternator or an oscillator. Inverters are oscillators. (Generators make DC).
Mixers -- When you simply connect the output of two oscillators at different frequencies, they will mix and produce both the outputs of each oscillator plus the two of them added together (A+B) as well as the difference between them (A-B). So a mixer simply connects the output of two different signals (perhaps one is an oscillator and one is a signal in which you're interested) and filters out all but the one you want.
Filters -- 3 kinds
Superheterodyne Receiver -- In a superheterodyne receiver, the signal from the antenna (around .2 - 50 microvolts - or millionths of a volt) is amplified in the radio frequency (RF) amplifier stage. The output of the RF stage is one input of a mixer. A Local Oscillator (LO) is the other input. In most cases, this first local oscillator is a variable frequency oscillator (VFO) (that is, it either has a tuning knob, usually a variable capacitor or it is a digital frequency synthesizer so it can produce whatever frequency is asked of it by a microprocessor so that your receiver tunes different frequencies. If there are different bands, they are also chosen here. A mixer is a small circuit with two inputs, A and B (or whatever you'd like to call them) and it produces two outputs, A+B and A-B. Since, in a receiver, we don't care about the A+B signal, it is filtered out. The A-B output of the mixer is at the Intermediate Frequency (IF) often around 10.7 Mhz, depending on to what particular frequency of a band to which you've tuned. A second mixer stage converts the signal to a second IF frequency, typically 455 KHz. There's often an automatic gain control which listens at the IF and if the signal gets too loud, it tells the RF Preamplifier to quiet down for a moment and then it goes back to receiving. The signal is then demodulated (demod). The modulation technique is irrelivent -- it might be AM, FM or SSB. The simpleist would be to just use a single diode as a decoder and then send it to an audio amplifer and a speaker to hear AM signals. Just a tiny bit more complicated than that, you could mix a carrier with a Beat Frequency Oscillator (a simple audio tone) to output CW as a tone or SSB as a voice.
AM -- Amplitude Modulation
The easiest way to describe the root of almost all of the world's problems is to observe that you cannot jail a billionaire.
Richard Nixon created the Petrodollar. Basically, rather than continue to peg the US Dollar to $35 per ounce of gold, Nixon needed to pay for wars and social programs and for that he needed to print way more dollars than he could without dumping the gold standard.
Now, the whole system is falling apart and that is causing a lot of the world's current tensions. The Criminal syndicate which forces every country (except those 3) in the entire world to have central banks which are beholden to the International Bank of Settlements (and the World Bank and International Monetary Fund along with the monsters who own the US Federal Reserve) is worried and flexing it's muscles by, among other things, trying to:
Ruin Western Europe by forcing a mass third-world migration of people who believe strongly in 6th century conquering and the setting up of a new Califate to destroy European Culture, and
Trying to get US persons to disarm and
Trying to institute international fascism by forcing us all into trade deals which allow multinational corporations to overrule our own health and safety and environmental and labor laws.
If I've made any mistakes, please Call me or email Kila or you can call us directly at (707) 413-6435. Here is my main website.