The web can provide you with lots of useful information, but also with even more rubbish. You might want to build an amplifier and stumble upon: http://tymkrs.tumblr.com/post/13115454729/beta-hfe-gain-2n3904s-i-think-its-transistor What goes wrong when you follow this advice? An excerpt:
A 2N3904 transistor’s beta max value is 150 and min value is 100. When figuring out DC current gain, the beta value is part of the formula. In the sheet above, it is also known as as hFE. (hFE = beta = gain for easier understanding) So if you need to build an amplifier with a gain of 300, you set up 3 transistor stages. A good rule of thumb is to build it using the minimum beta value instead of the max: [100] + [100] + [100] = 300…So even if it’s at its minimum, it still has enough gain [150] + [150] + [150] = 450…If all of the transistors were at their max, gain = 450 If you based the gain off of the maximum beta value instead of minimum: [150] + [150] = 300…. This is possible if it works at its maximum gain BUT [100] + [100] = 200…. This wouldn’t give you enough gain! Now hFE and beta cannot be greater in value than allowed by the gain. Otherwise you get noise caused by saturation and clipping of the signal