A 12 V DC source is connected through resistor R₁ = 2.2 kΩ to a node X. From node X to the source’s negative terminal there are two parallel paths: resistor R₂ = 10 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 green LED with a forward voltage of 2.2 V runs from a 12 V supply through a series resistor. Find the resistance R that sets the LED current to 15 mA.
An NPN transistor with β = 200 has voltage-divider bias from VCC = 12 V: R₁ = 39 kΩ from VCC to the base and R₂ = 15 kΩ from the base to ground. The collector resistor is RC = 1.5 kΩ and the emitter resistor is RE = 1 kΩ. 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.
A 9.1 V Zener regulator is fed from 15 V through 100 Ω and supplies a 680 Ω load. Find the Zener current IZ.
An NPN transistor with β = 150 switches a 150 Ω load resistor connected between VCC = 12 V and its collector. The emitter is grounded. The base is driven from a 5 V logic output through a base resistor RB. Take VBE = 0.7 V and VCE(sat) = 0.2 V. Find the largest base resistor RB, in kΩ, that still drives the transistor just into saturation.
An NPN transistor with β = 100 switches a 220 Ω load resistor connected between VCC = 9 V and its collector. The emitter is grounded. The base is driven from a 5 V logic output through a base resistor RB = 100 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.
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