# What are these types of logic diagrams called?

They are not quite "logic circuits" because when I look that up I get mostly the ones with logic gates drawn, not the transistors and such like these.

Also if I wanted to find a book that would teach me specifically about transistors and understand these types of circuits specifically, not digital systems in general, what should I look for? Any recommendations?

• these are not logic diagrams at all Feb 5, 2020 at 0:14
• I think you could start with Don Lancaster's RTL Cookbook. That link is owned by Don, himself. So feel free to use it. It's safe and you have his permission. (I think he's still alive.) Last time I talked with him was a decade ago, though. (He's kind of a "dry" conversationalist, my opinion.)
– jonk
Feb 5, 2020 at 6:25
• These are electronic circuits (technically circuit diagrams but everyone I know just call them circuits) - one step below logic diagrams. Feb 5, 2020 at 9:32
• I would add that it actually says on the picture.... a bar is just shorthand for "not a" likewise; . is or and + is and Feb 5, 2020 at 20:21
• @SpehroPefhany It was more than 10 yrs ago. I wanted to talk about some aspects that had hit on multiple levels for me. Turns out, I had picked up on something he'd spent time specifically trying to achieve and had worked hard at. He talked about what he'd done and we chatted about what makes for good technical communication. One example was his use of cartoons that separately told a story without needing to read the text. You could get a lot by skimming through the artwork. Also, the text worked too without needing the artwork. I think we spent 90 minutes on the phone, or so. I enjoyed it.
– jonk
Feb 5, 2020 at 23:14

It was a simple question. Requires a simple answer...

TTL

Transistor to transistor logic...

• No, these are not TTL gates, they are RTL gates. Feb 6, 2020 at 20:55
• The question was, "What are these types of logic diagrams called?", not what type of logic is it. Apart from this, a quick look at Transistor-transistor logic and Resistor-transistor logic will show that the answer is incorrect. Unfortunately the OP is happy with this! Feb 6, 2020 at 21:04
• "It was a simple question. Requires a simple answer..." I don't agree, answers on SE should be correct, not tailored to the knowledge of the OP. your answer is incorrect. Feb 11, 2020 at 17:41

Figure 1. Simple logic gates made of discrete NPN transistors and resistors.

This are schematics of simplified logic gates built using discrete components. From left to right they are NOT, NAND and NOR.

simulate this circuit – Schematic created using CircuitLab

Figure 2. Logic gate symbols NOT, NAND and NOR.

The symbolic representations allow the designer to concentrate on the logic operation rather than the electronic operation of the circuit.

Table 1. Truth table for NOT.

a    NOT
--------
0     1
1     0


Table 2. Truth table for NAND and NOR.

a    b   NAND    NOR
---------------------
0    0    1       1
1    0    1       0
0    1    1       0
1    1    0       0


(edited truth table)

• In discussion you can distinguish between the two kinds of diagrams by saying "transistor level diagram" and "gate level diagram". Feb 5, 2020 at 21:56

This looks like a circuit schematic diagram.

What would you like to know about transistors exactly?

The ones shown in your diagram are called NPN transistors.

They consist of three pins: base, collector and emitter.

A small current applied to the base of the transistor creates a much larger current between the collector and the emitter.

Therefore they can be used as both switches and amplifiers.

You could always just Google transistors and see the different types.

• Great answer - confronting the basics! Feb 5, 2020 at 16:18
• "Two NPN transistors together are known as the Darlington configuration" Nope. Neither configuration is a Darlington, where the emitter of one transistor feeds the base of the second, and the collectors of both are tied together. Feb 5, 2020 at 18:16
• I just stated Darlington configuration to give an example of transistors and how they work. Not saying the above diagram is a Darlington configuration. Feb 5, 2020 at 18:20

As others have said, those in the picture are in fact schematics, or schematic diagrams. They represent with symbols actual, physical components with their connections.

I'd like to add one more detail regarding the specific type of circuits represented in the pictures. They are a form of logic gates (it depends on the input signals, but that's the meaning of the captions), built with the resistor-transistor logic (RTL). Compared with complementary logic (or TTL by transistor-transistor logic), the RTL logic only uses pull-down or pull-up transistors with the other branch made by a resistor. This simplifies the circuitry, at the expense of performance (speed, area, power efficiency).

I think you are looking for Schematic Diagrams - they show the detailed connections between individual components - transistors, resistors, capacitors, etc.

If you are using digital integrated circuits, a schematic will show the gated symbols. In schematics, more complex ICs will be shown as blocks with many connections.

The sketches you show are simple schematic diagrams.

I read the original requests as the OP wanting some reasonable search terms (for Googling, for instance) to find schematic diagrams of circuits that implement logic gates.

His problem is that unfortunately "logic gate circuits", would generally yield circuits that use logic gates rather than circuits that implement logic gates.

This would appear to be analogous to "audio amplifier circuits", but this search would more likely actually provide circuits that implement amplifiers.

This sort of ambiguity can turn up any time you use a noun to modify another noun with no preposition or other phrasing to connect them.

It is an ambiguous form of the distinction between a "cardboard box" (a box made of cardboard) and a "shoe box" (a box made to contain shoes). This example is unambiguous because one does not generally store or pack cardboard in a box, nor does one generally makes boxes out of shoes.

But because circuits can be used in a modular manner within more complex circuits terms like "logic gate circuit" are much more ambiguous.

Having said all this, no I don't have a solution to this problem. Even appropriate use of prepositions and such likely would not help because these tend to be ignored by search engines.

Discrete component transistor port logic.