Junction transistor: structure and action (pnp, npn)
Transistors and circuits · Physics
DC circuit
Interactive 3DElectrons drift around the loop — raise the voltage and watch the current obey Ohm's law.
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V
1V12V
Study notes
An n-p-n transistor has β = 100. The base current is 40 µA. (a) Find I_C and I_E. (b) If the collector resistor is 2 kΩ with a 12 V supply, find V_CE (ignore saturation). Solution: (a) I_C = β·I_B = 100 × 40 µA = 4.0 mA. I_E = I_C + I_B = 4.04 mA. (b) Drop across R_C = 4.0 mA × 2 kΩ = 8.0 V. V_CE = 12 − 8.0 = 4.0 V — the transistor is in active mode (V_CE > ~0.2 V), consistent with our assumption.