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Date: 23-10-2020
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DYNAMIC CURRENT AMPLIFICATION
Another way of specifying current amplification is as the ratio of a difference in IC to a small incremental difference in IB that produces it. This is the dynamic current amplification, also known as current gain. It is customary to abbreviate the words the difference in by the uppercase Greek letter delta (Δ) in mathematical expressions. Then, according to this definition,
Current gain = ΔIC/ΔIB
The ratio ΔIC/ΔIB is greatest where the slope of the characteristic curve is steepest. Geometrically, ΔIC/ΔIB at any given point on the curve is the slope of a line tangent to the curve at that point. When the operating point of a transistor is on the steep part of the characteristic curve, the device has the largest possible current gain, as long as the input signal is small. This value is close to HFE. Because the characteristic curve is a straight line in this region, the transistor can serve as a linear amplifier if the input signal is not too strong. This means that the output signal waveform is a faithful reproduction of the input signal waveform, except that the output amplitude is greater than the input amplitude.
As the operating point is shifted into the part of the characteristic curve where the graph is not straight, the current gain decreases, and the amplifier becomes nonlinear. The same thing can happen if the input signal is strong enough to drive the transistor into the nonlinear part of the curve during any portion of the signal cycle.
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تفوقت في الاختبار على الجميع.. فاكهة "خارقة" في عالم التغذية
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أمين عام أوبك: النفط الخام والغاز الطبيعي "هبة من الله"
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جمعية العميد تناقش التحضيرات النهائية لمؤتمر العميد الدولي السابع
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