Okay.
Yes, in most cases "close enough" works just fine. As has been stated, within 10% is usually fine. In most cases the difference will be unnoticeable or subtle. The three types of resistors you'll see most used are those with 10%, 5% or 1% tolerance, and more specifically 5% carbon film or 1% metal film. If your substituted value is within 5% don't even worry about it. But like Induction said, it depends on what you're doing, because as innocuous as it may seem to alter a value by 10%, it can have effects ranging from slightly shifting your tone to completely mucking up your biasing.
Most diodes, at least the commonly used (and not just by our kind) silicon small-signal and rectifier diodes, use the 1NXXXX naming convention. It's really just a convention, same with the 2NXXXX convention with transistors. The ones you should know about are
1. 1N4148 and similar. As of a number of years ago equivalent to the 1N914, the most common small-signal diode in use likely across the electronics industry. Has a forward voltage of ~0.7V, and can handle 50-75V reverse and 500mA of current. Used widely for clipping and rectification of small signals.
2. 1N400x series. Common rectifier diodes usually used in higher-power applications. The one we tend to use is the 1N4001, because it's physically the smallest and already way de-rated for our applications. Increasing suffix number (i.e. 1N4002, 1N4004, 1N4007) indicate increasing voltage rating; they all handle 1A.
3. 1N581x series. Slightly less common Schottky rectifier diodes, this just means they have a lower forward voltage drop than the "regular" diodes. We use the 1N5817 as series polarity protection so we get less loss of supply voltage. Again, increasing suffix number (1N5818, 1N5819) indicate increasing voltage rating. You'll sometimes see the 1N5818 used in 18V and up circuits.
4. There's a slew of different types of germanium diode out there. Commonly used parts are 1N34A, 1N60/1N60P, 1N270, D9x, SFDxxx, and so on. The use of these are less clear-cut because most are used in clipping applications and so are subjective.
5. Zener diodes. These are diodes that actually let reverse current flow if the voltage is above their breakdown voltage. So if you have a 9.1V Zener diode, it will conduct like a normal diode until the voltage hits 9.1V, under which circumstances it will begin to let current flow in the opposite direction. They tend to be used as simple voltage regulators and for overvoltage protection, especially of static-sensitive components like MOSFETs.
Also something to note is that a diode does not necessarily "stop current", but rather only allows it to flow in one direction.
The 1N4739A is a
type of 9.1V Zener, but not the
only 9.1V Zener in the world. If a 9.1V Zener is called for then any one will work presuming the power handling is sufficient. 1W is definitely sufficient for this application.
It's just fine to use a 1N5818 in place of a 5817, all that's different is the voltage capacity.
Through all the worry and pain we move on
Locked
