A p-n photodiode is fabricated from a semiconductor with a band gap of 2.5 eV. It can detect a signal of wavelength:

1. 6000 Å

2. 4000 nm

3. 6000 nm

4. 4000 Å

 

The circuit is equivalent to: 
 

1. AND gate

2. NAND gate

3. NOR gate

4. OR gate

In the following circuit, the output Y for all possible inputs A and B is expressed by the truth table: 
    
 

The figure shows a logic circuit with two inputs \(A\) and \(B\) and the output \(C\). The voltage waveforms across \(A\), \(B\), and \(C\) are as given. The logic circuit gate is:
   

1. \(\mathrm{OR}\) gate
2. \(\mathrm{NOR}\) gate
3. \(\mathrm{AND}\) gate
4. \(\mathrm{NAND}\) gate

\({C}\) and \({Si}\) both have the same lattice structure, having \(4\) bonding electrons in each. However, \(C\) is an insulator whereas \(Si\) is an intrinsic semiconductor. This is because:

Zener breakdown will occur if:
1. impurity level is low.
2. impurity level is high.
3. impurity is less on the n-side.
4. impurity is less on the p-side.

The logic behind the 'NOR' gate is that it gives:

In a transistor circuit shown here, the base current is  35 $\mathrm{\mu }$A  and the potential difference across emitter-base junction is 4.5 V. The value of the resistor R_b is:
                 

1. 128.5 k$\mathrm{\Omega }$

2. 257 k$\mathrm{\Omega }$

3. 380.05 k$\mathrm{\Omega }$

4. None of these

In a transistor, a change of 8.0 mA in the emitter current produces a change of 7.8 mA in the collector current. What change in the base current is necessary to produce the same change in the collector current?
1. 50 $\mathrm{\mu }$A 
2. 100 $\mathrm{\mu }$A
3. 150 $\mathrm{\mu }$A 
4. 200 $\mathrm{\mu }$A

An NPN transistor conducts when: