"Standard" components...?
Here are the types I immediately think of when someone says "diode", "op-amp", ...
- Op-amp : LM741. The first "easy to use" op-amp IC on the market.
- Diode : 1N4001. General purpose silicon diode good up to 50V blocking voltage and 1 amp current. The 1N4002, 1N4003, etc. are similar diodes with higher voltage ratings.
- Transistor: 2N2222. NPN bipolar junction transistor. The 2N2907 is apparently the PNP equivalent.
- (Linear) Voltage regulator : LM78xx series, i.e. the LM7805 for 5 V, the LM7812 for 12 V.
- Digital logic, i.e. NAND gates and so on: 7400 series and 4000 series.
These are extremely common, basic parts. If you walked into a hobby store and asked for a hundred transistors, without specifying anything else, you would probably get a bag of 2N2222's.
This is not to say these parts are useful for everything - they have limitations on voltage, current, speed, accuracy, and so forth. But if you have to pick a type of component for the purposes of a SPICE simulation, these will work fine.
Edit: For reference, here are the "default parts" you get in CircuitLab:
- Op-amp
TL081 - Diode
1N4148 - Zener diode
1N4733A - NPN BJT
2N3904 - PNP BJT
2N3906 - N-channel MOSFET
IRF530 - P-channel MOSFET
IRF9530 - N-channel JFET
J310 - P-channel JFET
J271
See TUP TUN DUS DUG for a list of "universal" small-signal transistors and diodes often used interchangeably in example circuits published (e.g.)
Here is a link to a scan of an original page by Elektor Magazine, who coined the phrase TUP TUN DUS DUG. They hardly use it today (and some of the parts may have become obsolete), but it is still a valid concept and it's good to know where it came from. If you're planning a design, today, with second source parts in mind, you're doing essentially the same thing.
What people think of as the "common" or "basic" transistor is generally an NPN small-signal BJT but the exact type varies from place to place and over time. As an occasional hobbyist I used to use BC108 then BC547 but I'd buy anything cheap (e.g.) and I'm used to seeing 2N3704 and translating that to BC547 with the leads in the wrong order.
There doesn't seem to be an equivalent "universal" small-signal MOSFET?
By comparison, the 1N4148 is much more uniformly found in examples.
The 741 opamp seems to hold a similar position even though apparently it is usually not a good choice anymore.
When referring to a generic (rather than standard) op amp, diode, transistor etc. its about the basic function of the device without considering specific circuit criteria such as voltage range, power consumption, speed of operation etc.
For example. If you take the 'op amp' you would expect a device to have two inputs (inverting and non inverting), have a high open loop gain, have high impedance inputs and a low impedance output. You would also expect it to perform predictably in 'standard circuits' such as inverting / non inverting amplifier, integrator / differentiator, comparator etc.
In other words virtually any op amp can be used as a plug in replacement and still work.
For specific applications it might be important that the output has full range or the frequency bandwidth has a high value or it can be used a low single supply voltage. In that case you would specify the device type to be used in the circuit.
Generic diodes are either small signal types used for detecting AC signals or rectifier types - used for power supply AC/DC conversion. Even here you usually have to state Silicon or Germanium type.
Specific diodes will be chosen by voltage, current, frequency, construction etc.
Generic transistors - (NPN or PNP) are sorted initially by power rating - small signal, medium power or high power. It will be assumed that the gain for a small signal type will be a least 100 and the high power type will have a gain of about 10. A typical small signal (NPN) type could be a 2N2222
Of course for specific circuits you need to consider voltage ratings, frequency range etc.