LED Characteristics MCQs : This section focuses on the "LED Characteristics". These Multiple Choice Questions (MCQs) should be practiced to improve the LED Characteristics skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.
Question 1
Determine CW operating lifetime for LED with βrt = -0.58 and degradation rate βr = 7.86*10-11 h-1.
A. 32.12
B. 42
C. 22.72
D. 23.223
Question 2
Determine degradation rate βrif constant junction temperature is 17 degree celsius.
A. 7.79*10-11
B. 7.91*10-11
C. 6.86*10-11
D. 5.86*10-11
Question 3
Determine the 3 dB electrical bandwidth at 3 dB optical bandwidth Bopt of 56.2 MHz.
A. 50.14
B. 28.1
C. 47.6
D. 61.96
Question 4
For particular materials with smaller bandgap energies operating in _____________ wavelength, the linewidth tends to ______________
A. 2.1 to 2.75 μm, increase
B. 1.1 to 1.7 μm, increase
C. 2.1 to 3.6 μm, decrease
D. 3.5 to 6 μm, decrease
Question 5
In optical fiber communication, the electrical signal dropping to half its constant value due to modulated portion of optical signal corresponds to _______
A. 6 dB
B. 3 dB
C. 4 dB
D. 5 dB
Question 6
Intrinsically _________________ are a very linear device.
A. Injection lasers
B. DH lasers
C. Gain-guided
D. LEDs
Question 7
Linearizing circuit techniques are used for LEDs.
A. TRUE
B. FALSE
Question 8
The 3 dB electrical bandwidth B is 42 MHz. Determine 3dB optical bandwidth Bopt.
A. 45.18
B. 59.39
C. 78.17
D. 94.14
Question 9
The internal quantum efficiency of LEDs decreasing _______________ with ________________ temperature.
A. Exponentially, decreasing
B. Exponentially, increasing
C. Linearly, increasing
D. Linearly, decreasing
Question 10
The optical bandwidth is _____________ the electrical bandwidth.
A. Smaller
B. Greater
C. Same as
D. Zero with respect to
Question 11
The optical power at 20 MHz is 246.2 μW. Determine dc drive current applied to device with carrier recombination lifetime for LED of 6ns.
A. 3.48*10-4
B. 6.42*10-9
C. 1.48*10-3
D. 9.48*10-12
Question 12
To utilize _____________________ of SLDs at elevated temperatures, the use of thermoelectric coolers is important.
A. Low-internal efficiency
B. High-internal efficiency
C. High-power potential
D. Low-power potential
Question 13
When a constant d.c. drive current is applied to device, the optical o/p power is 320 μm. Determine optical o/p power when device is modulated at frequency 30 MHz with minority carrier recombination lifetime of LED i.e. 5ns.
A. 4.49*10-12
B. 6.84*10-9
C. 1.29*10-6
D. 2.29*10-4