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 = 1 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 5 V DC source drives current through a 330 Ω resistor in series with two forward-biased silicon diodes. Use the constant-drop model with 0.7 V per conducting diode. Find the current I in mA.
An NPN transistor with β = 200 has voltage-divider bias from VCC = 20 V: R₁ = 56 kΩ from VCC to the base and R₂ = 10 kΩ from the base to ground. The collector resistor is RC = 1 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.
3 green LEDs (forward voltage 2.2 V each) are connected in series with a resistor to a 9 V supply. Find the resistance R that sets the current to 10 mA.
A diode is modelled as 0.65 V in series with 5 Ω (it conducts above 0.65 V). It is in series with a 1000 Ω resistor across a 6 V supply. Find the operating current ID where the diode line meets the load line.
An NPN transistor with β = 200 switches a 330 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. Take VBE = 0.7 V and VCE(sat) = 0.2 V. For reliable switching, design for a base current 2 times the minimum needed for saturation. Find RB in kΩ.
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