A 15 V DC source is connected through resistor R₁ = 680 Ω to a node X. From node X to the source’s negative terminal there are two parallel paths: resistor R₂ = 4.7 kΩ, and a silicon diode with its anode at X. Use the constant-drop model with 0.7 V. Find the diode current ID in mA.
A red LED with a forward voltage of 2 V runs from a 12 V supply through a series resistor. Find the resistance R that sets the LED current to 10 mA.
An NPN transistor with β = 200 has voltage-divider bias from VCC = 12 V: R₁ = 56 kΩ from VCC to the base and R₂ = 15 kΩ from the base to ground. The collector resistor is RC = 2.7 kΩ and the emitter resistor is RE = 680 Ω. Take VBE = 0.7 V and use the Thévenin equivalent of the divider (do not neglect the base current). Find the collector–emitter voltage VCE.
An NPN transistor with β = 150 has voltage-divider bias from VCC = 12 V: R₁ = 82 kΩ from VCC to the base and R₂ = 12 kΩ from the base to ground. The collector resistor is RC = 2.7 kΩ and the emitter resistor is RE = 680 Ω. Take VBE = 0.7 V and use the Thévenin equivalent of the divider (do not neglect the base current). Find the collector current IC in mA.
An NPN transistor with β = 150 switches a 100 Ω load resistor connected between VCC = 24 V and its collector. The emitter is grounded. The base is driven from a 3.3 V logic output through a base resistor RB = 1 kΩ. Take VBE = 0.7 V and VCE(sat) = 0.2 V. Find the collector current IC in mA when the input is high. Decide first whether the transistor is saturated.
A 5.6 V Zener regulator must supply up to 20 mA to a load. The input can drop to 20 V, and the Zener needs at least 5 mA to regulate. Find the largest series resistance Rmax that keeps it regulating.
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