# Electrical Engineering Assignment: DC Gate Voltage (Multiple Choice Questions Sample)

PLEASE WRITE DOWN ALL THE PROCESS! THANKS

15 sub questions. That is why this order is 15 questions but it is only 6 problems.

Problem 2

The DC drain current of the MOSFET in the audio amplifier circuit shown in the figure is 500 µA. Find the lower −3 dB frequency of the circuit. For full credit, show all work including the following:

Solution

Since the DC gate voltage current is 0, the DC voltage at the source terminal can be calculated as

VS = -VGSQ, and the gate to source voltage is determined from

IDQ = IQ = Kn (VGSQ-VTN)2

Alternatively, 0.5 = (0.5) (VGSQ – 1)2 which yields VGSQ = - VS = 2

Therefore, VGSQ = VDD – IDQRD -VS= 5 - (1)(2) - (-2) = 5V

The transistor is therefore biased in the saturation region

The small signal equivalent circuit is shown below

Vo = -gmVgsRD

Since Vgs = Vi, the small signal voltage gain is

Av = Vo/Vi = -gmRD = -(1.414) (2) = 2.828

FL = 1/ 2πRC

= 1 / 2 x π x 602 x 10

= 2.642 x 10-5 Hz

Problem 3

In these questions, “place its break frequency” means that the capacitor value in question is calculated independently of the other break frequencies. In other words, each of the capacitance values is calculated by considering the other capacitances to be short-circuits.

At low frequencies, we use the coupling capacitors C1, C2, and C3

Ic(DC) = (β/ β+1) IE

= (100/101) mA = 0.99mA

Therefore, =100/0.99 x 26mV = 2.626 k Ω

For C1

RTh1 = 10k + [2.55k] = 12.55 k Ω

Therefore, f1 = 1/ (2π RTh1 C1) C1 = 1/ (2πx12.55x103 x20Hz)

= 6.34 x 10 -7

Therefore, C1 = 0.643µF

For C2

In this case, C1 and C3 are shorter:20Hz

f1 = 1/ (2π RTh2 C2)

C2 = 1/ (2π (10k + 10k) x 20Hz)

= 3.97 x 10 -7

Therefore, C2 = 0.397µF

For C3

In this case, C1 and C2 are shorter:200Hz

Where ib = (0 – 1) V/ (10k // 100k) + 2.626k

= RTh3 = 1/ Ix

= - [10k // 100 k] + 2.626/- (101)

= 9.09k +

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- Electrical Engineering Assignment: DC Gate VoltageDescription: The DC drain current of the MOSFET in the audio amplifier circuit shown in the figure is 500 µA. Find the lower −3 dB frequency of the circuit...15 questions | No Sources | APA | Engineering | Multiple Choice Questions |