# How important are BJT characteristic curves when designing amplifiers?

I was going to make a voltage amplifier for weak signals with 2SD786, but I noticed that the manufacturers haven't included the characteristic curves in the datasheets. How can I optimize the circuit if I don't know this transistor well? For example, according to the datasheet $h_{FE}$ value is very different for different conditions. Should I try to generate the curves myself before using this transistor?

UPDATE:

Assume that for a given $V_{CC}$, you want to choose a good load line by choosing $R_L$. Also you should choose a good operating point on the load line by determining appropriate $I_B$. However you don't have the characteristic curves.

• What you need to identify is the circuit of the amplifier you might wish to use with this transistor. The actual target circuit defines how the transistor is used and whether the hFE limitations (as seen in all BJTs) might unduly affect desired performance. In other words, with a proper design, the transistor limitations are largely eradicated; with a poor design you have side-effects due to transistor limitations. – Andy aka Sep 2 '18 at 13:57
• Nice find - this would be a good preamp for a low-impedance signal source (likely not-so-good for a high-Z source). Data sheet suggests that low voltage noise requires a DC bias @ 10mA collector current. You can expect a fairly low amplifier input impedance biased this way. Also - be aware that many bipolar transistors meant for higher-power applications don't spec noise at all - and are at least as good as this one. – glen_geek Sep 2 '18 at 14:11
• @Andyaka, I wanted to get the most possible gain from this transistor and at the same time avoid distortions. If I know the transistor well, I can choose the right values for the resistors. – Arham Sep 2 '18 at 14:18
• Mutually exclusive requirements: most possible voltage gain and low distortion. More mutually exclusive requirements: most possible voltage gain and high temperature stability and drift. Show your circuit and take note of what will likely be said. – Andy aka Sep 2 '18 at 14:27
• @Andyaka, please see the UPDATE paragraph. – Arham Sep 2 '18 at 15:12