Looking at the curves, we can approximate the transistor’s gain parameter β for our desired operating-point of I CQ=5mA and V CEQ=10V. With the assumptions above, we can end up with the load-line (a.k.a. 2 arbitrarily depending on the application, just like the following. Secondly, we can choose the collector-emitter voltage and quiescent collector-current looking at Fig. We need to replace all capacitors with open-circuit (because of the fact that capacitors do not allow DC elements) and eliminate the unnecessary parts to have the following.Įvery circuit needs a supply, so I don’t see any reason stopping us from choosing V CC=20V for this one. The Base-emitter voltage and output characteristics shown below are enough information to go.Ĭlass-A design requires the transistor to be in its active region even when no input signal is provided. Options were limited, so i picked 2SC4102, a small current transistor from ROHM. Let’s start with defining the desired input-output requirements and load conditions of the amplifier.įor a simple tutorial, I decided to pick a transistor that has good datasheet and good pre-installed model in LTspice. It works with single supply and has DC-biasing stage as well as AC-coupling elements. While more detailed best-practice designs exist, the circuit above is the best for teaching purposes. Let’s see the circuit schematic for our amplifier.
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