Virtual Labs

1. What SPICE parameter is the primary model component for the stored minority charge in forward bias, which in turn determines the diffusion capacitance?

CJO

Explanation

TT

(Transit Time) Explanation

Explanation

VJ

(Junction Potential) Explanation

Explanation

M

(Grading Coefficient) Explanation

Explanation

2. How does the SPICE model describe the behavior of the depletion capacitance (

C_D

) as the applied reverse bias voltage (

V_R

) increases?

a: It decreases, varying inversely with the sum of the junction potential and reverse voltage, raised to the grading coefficient (M). Explanation

Explanation

b: It increases, varying directly with the sum of the junction potential and reverse voltage, raised to the grading coefficient (M). Explanation

Explanation

c: It decreases exponentially as the reverse voltage increases. Explanation

Explanation

d: It is calculated as the transit time multiplied by the change in forward current. Explanation

Explanation

3. For a linearly graded p-n junction, what value is the grading coefficient 'M' typically set to?

a: 0.5 Explanation

Explanation

b: 1.0 Explanation

Explanation

c: 0.33 Explanation

Explanation

d: 2.0 Explanation

Explanation

4. The diffusion capacitance (

C_{diff}

) in forward bias is modeled as being directly proportional to which two quantities?

a: Junction potential (

VJ

) and Transit time (

TT

) Explanation

Explanation

b: Zero-bias capacitance (

CJO

) and Forward current (

I_D

) Explanation

Explanation

c: Forward current (

I_D

) and Transit time (

TT

) Explanation

Explanation

d: Grading coefficient (

M

) and Junction potential (

VJ

) Explanation

Explanation

5. If a diode has a linearly graded junction (

M=0.33

), which plot would yield a straight line against the reverse voltage

V_R

, allowing for extraction of

VJ

log(C_J)

vs.

V_R

Explanation

1/C_J^2

vs.

V_R

Explanation

1/C_J^3

vs.

V_R

Explanation

C_J

vs.

V_R

Explanation

6. In the

1/C_J^2

vs.

V_R

plot for an abrupt junction, the slope of the linear region is inversely proportional to what physical parameter?

a: The junction area Explanation

Explanation

b: The built-in potential (

VJ

) Explanation

Explanation

c: The effective doping concentration Explanation

Explanation

d: The transit time (

TT

) Explanation

Explanation

7. What is the primary purpose of the SPICE parameter 'FC' (Forward-bias depletion capacitance coefficient)?

a: It models the frequency dependence of the capacitance. Explanation

Explanation

b: It provides a linear approximation for depletion capacitance under forward bias to prevent the model equation from becoming singular. Explanation

Explanation

c: It sets the transit time

TT

value. Explanation

Explanation

d: It models the capacitance in reverse breakdown. Explanation

Explanation

8. The transit time

TT

is typically extracted by measuring the diode's capacitance under which condition?

a: At zero bias (

V_D = 0

). Explanation

Explanation

b: Under strong reverse bias. Explanation

Explanation

c: Under strong forward bias, where

C_{diff}

dominates. Explanation

Explanation

d: During avalanche breakdown. Explanation

Explanation

9. Under what bias condition does the depletion capacitance (

C_D

) almost exclusively determine the total junction capacitance (

C_J

a: Strong forward bias Explanation

Explanation

b: Zero bias Explanation

Explanation

c: Reverse bias Explanation

Explanation

d: At

V_D = VJ

Explanation

10. What is the most direct way to measure the parameter

CJO

a: Measure the total capacitance

C_J

V_D = 0

V, typically at a fixed high frequency (e.g., 1 MHz). Explanation

Explanation

b: Measure the slope of the

C_J

vs.

I_D

curve in forward bias. Explanation

Explanation

c: Calculate it from the forward I-V curve's ideality factor. Explanation

Explanation

d: Extrapolate the

1/C_J^3

vs.

V_R

plot to

V_R = 0

. Explanation

Explanation

Extraction of diode SPICE parameters related to Capacitance-Voltage (C-V)