HPK taruh disini
The flow analogy can also be used to model how a transistor operates in a
logic circuit. The transistor is an amplifier. It uses a small amount
of energy to control a larger energy source, just as a valve controls a
high-pressure water source. There are two kinds of transistors: bipolar
and field-effect transistors (FETs).
We will look at bipolar transistors first; these amplify current. A small amount of current flows in the control circuit (the transistor base emitter circuit) to turn the transistor on. This control current is amplified (multiplied by the gain or beta of the transistor) and allows a larger current to flow in the output circuit (the collector emitter circuit). Once again, the device is not perfect because of the resistance, current, gain, and leakage limitations of real transistors. Bipolar transistors come in two polarities, NPN and PNP, with the difference being the direction in which current flows for normal operation. A bipolar PNP transistor is shown and modeled in Figure 1-7.
For most of the illustrative circuit examples in this site, we will be using NPN transistors, as shown in Figure 1-8.
We will look at bipolar transistors first; these amplify current. A small amount of current flows in the control circuit (the transistor base emitter circuit) to turn the transistor on. This control current is amplified (multiplied by the gain or beta of the transistor) and allows a larger current to flow in the output circuit (the collector emitter circuit). Once again, the device is not perfect because of the resistance, current, gain, and leakage limitations of real transistors. Bipolar transistors come in two polarities, NPN and PNP, with the difference being the direction in which current flows for normal operation. A bipolar PNP transistor is shown and modeled in Figure 1-7.
