Question

An 11.5 V zener diode (11.5 V at 25 deg C) has a negative temperature coefficient of 0.05%/ deg C What is the zener voltage at 85 deg C.

a. 12.3317
b. 11.5117
c. 11.155 V
d. 15.551 V​

Answer 1

Given:

An 11.5 V Zener diode (11.5 V at 25 degree C) has a negative temperature coefficient of 0.05%/ degree/C.

To Find:

What is the Zener voltage at 85 degree C?

a. 12.3317 V

b. 11.5117  V

c. 11.155 V

d. 15.551 V​

Solution:

given, initial voltage,V1 = 11.5V

T1 = 25 degree,

T2 = 85 degree.

coefficient of temp. , Cz = - 0.05%

Since, we know that - final voltage of Zener diode is given by

$V_{2}=V_{1}[1+C_{z}*(T_{2}-T_{1})]$

on substituting values, we get

$V_{2}=11.5[1+\dfrac{-0.05}{100}*(85-25)]\\\\V_{2}=11.5[1-0.03]\\\\V_{2}=11.155 \ V$

Hence, Zener voltage at 85 degree is 11.155V.

option (c) is correct.