31. They are useful in amplifiers because the currents at the emitter and collector are controllable by a relatively small base current . 32. Importantly, the large flow varied proportionally in relation to the size of the small base current , allowing all kinds of amplification. 33. In active mode, the ratio of the collector current to the base current is called the " DC current gain ". 34. In a BJT circuit, the BJT has a different current-voltage ( I C-V CE ) characteristic depending on the base current . 35. Placing a series of these curves on the graph shows how the base current will affect the operating point of the circuit. 36. In the example light-switch circuit shown, the resistor is chosen to provide enough base current to ensure the transistor will be saturated. 37. A lower base-resistor voltage drop reduces the base current , which results in less collector current because I c = ? I B. 38. First Aid, which sells for about $ 35, also will update itself via the Internet, so you can keep its knowledge base current . 39. It is possible to connect a floating source between the two bases, but it is necessary to ensure paths for the biasing base currents . 40. In this region, I c = ?I b where Ic is collector current and Ib is base current , following linear relation y = mx.
