hum of current, it has to dutifully replicate a person s voice, or an entire symphony. Luckily, a semiconductor is perfectly suited to this job. It is exquisitely sensitive to how many extra or missing electrons are inside Each time the input signal shoves more holes into the germanium, it changes the way current flows across the crystal-the output current instantly gets larger and smaller, perfectly mimicking the input (after Public Broadcasting System(PBs)television series, 1999 OE F Schubert, Rensselaer Polytechnic Institute, 2003© E. F. Schubert, Rensselaer Polytechnic Institute, 2003 7 hum of current, it has to dutifully replicate a person’s voice, or an entire symphony. Luckily, a semiconductor is perfectly suited to this job. It is exquisitely sensitive to how many extra or missing electrons are inside. Each time the input signal shoves more holes into the germanium, it changes the way current flows across the crystal - the output current instantly gets larger and smaller, perfectly mimicking the input.” (after Public Broadcasting System (PBS) television series, 1999)