Electronic Devices
- In a common emitter transistor amplifier the audio signal voltage across the collector is 3 V. The resistance of collector is 3 kΩ. If current gain is 100 and the base resistance is 2 kΩ, the voltage and power gain of the amplifier is : Answer: 2. 150 and 15000 Key idea: in a common emitter amplifier, voltage gain A_v=βR_C/R_B and power gain =β A_v . A_v=100×3\ kΩ/2\ kΩ=150... 1
- What is the output Y in the following circuit, when all the three inputs A, B, C are first 0 and then 1? Answer: 2. 1, 0 Gate P is an AND gate on A and B; gate Q is a NAND gate whose inputs are P's output and C. So Y=(A· B)· C . A = B = C = 0: P... 1
- The given circuit has two ideal diodes connected as shown in the figure below. The current flowing through the resistance R_1 will be Answer: 4. 2.5 A An ideal diode conducts only when forward biased. From the figure, the battery drives current through R₁ and then to the tw... 1
- For CE transistor amplifier, the audio signal voltage across the collector resistance of 2 kΩ is 4 V. If the current amplification factor of the transistor is 100 and the base resistance is 1 kΩ, then the input signal voltage is Answer: 1. 20 mV In a CE amplifier, V_out=I_CR_C and I_C=β I_B ; input voltage is V_in=I_BR_B . I_C=4/2000=2 mA. I_B=I_C/β=2\ mA/100=20\ μA... 1
- To get output 1 for the following circuit, the correct choice for the input is : Answer: 4. A = 1, B = 0, C = 1 Key idea: from the circuit, Y=(A+B)· C : A and B go to an OR gate, and its output goes to an AND gate with C.... 1
- Consider the junction diode as ideal. The value of current flowing through AB is : Answer: 2. 10⁻² A Key idea: check whether the ideal diode is forward or reverse biased. A is at +4 V (on the p-side) and B at -6 V, so the d... 1
- A npn transistor is connected in common emitter configuration in a given amplifier. A load resistance of 800 Ω is connected in the collector circuit and the voltage drop across it is 0.8 V. If the current amplification factor is 0.96 and the input re… Answer: 1. 4, 3.84 Key idea: in common emitter, A_v=βR_L/R_i and power gain =β A_v . The question uses 0.96 as the current gain β in these f... 1