Transistor Amplifier Calculator - paulorenato Transistor Amplifier Calculator. For simple Do-It-Yourself amplifiers such as the one described under my Karaoke Mixer project, I often turn to the circuit topology in Figure 1. The biasing scheme in Figure 1 is certainly not the most stable of the possible schemes. BJT Transistor Biasing Calculator - Peter Vis BJT Transistor Biasing Calculator This calculator will compute the values of the biasing resistors required to provide the maximum output voltage swing in a NPN bipolar junction transistor (BJT) amplifier circuit. The algorithm makes use of AC and DC load line theory and formulas and is one of the most accurate you will find online.